{"id":301337,"date":"2023-12-30T20:55:31","date_gmt":"2023-12-30T13:55:31","guid":{"rendered":"https:\/\/hoanghamobile.com\/tin-tuc\/?p=301337"},"modified":"2023-12-30T20:55:31","modified_gmt":"2023-12-30T13:55:31","slug":"chu-vi-hinh-tu-giac","status":"publish","type":"post","link":"https:\/\/hoanghamobile.com\/tin-tuc\/chu-vi-hinh-tu-giac\/","title":{"rendered":"C\u00f4ng th\u1ee9c t\u00ednh chu vi h\u00ecnh t\u1ee9 gi\u00e1c: L\u00fd thuy\u1ebft, c\u00e1c d\u1ea1ng to\u00e1n v\u00e0 b\u00e0i t\u1eadp c\u00f3 l\u1eddi gi\u1ea3i"},"content":{"rendered":"

C\u00f4ng th\u1ee9c t\u00ednh <\/span>chu vi h\u00ecnh t\u1ee9 gi\u00e1c <\/b>nh\u01b0 th\u1ebf n\u00e0o? V\u1ed1n d\u0129 h\u00ecnh h\u1ecdc c\u00f3 r\u1ea5t nhi\u1ec1u bi\u1ebfn th\u1ec3 kh\u00e1c nhau n\u00ean c\u00f4ng th\u1ee9c t\u00ednh c\u1ee7a r\u1ea5t \u0111a d\u1ea1ng. Ch\u00ednh v\u00ec v\u1eady, nh\u1eb1m m\u1ee5c \u0111\u00edch gi\u00fap b\u1ea1n \u0111\u1ecdc hi\u1ec3u r\u00f5 h\u01a1n v\u1ec1 l\u00fd thuy\u1ebft t\u00ednh chu vi, c\u0169ng nh\u01b0 c\u00f3 th\u1ec3 \u00e1p d\u1ee5ng \u0111\u01b0\u1ee3c c\u00f4ng th\u1ee9c v\u00e0o th\u1ef1c t\u1ebf. Ngay b\u00ean d\u01b0\u1edbi \u0111\u00e2y Ho\u00e0ng H\u00e0 Mobile \u0111\u00e3 t\u1ed5ng h\u1ee3p cho b\u1ea1n nh\u1eefng th\u00f4ng tin quan tr\u1ecdng nh\u1ea5t, c\u00f3 bao g\u1ed3m b\u00e0i t\u1eadp t\u00ednh chu vi v\u00e0 l\u1eddi gi\u1ea3i. M\u1eddi b\u1ea1n c\u00f9ng xem qua v\u00e0 n\u00e2ng cao ki\u1ebfn th\u1ee9c v\u1edbi ch\u00fang t\u00f4i nh\u00e9.<\/span><\/p>\n

H\u00ecnh t\u1ee9 gi\u00e1c l\u00e0 g\u00ec?<\/b><\/h2>\n

M\u1ed9t h\u00ecnh t\u1ee9 gi\u00e1c \u0111\u01a1n gi\u1ea3n l\u00e0 m\u1ed9t h\u00ecnh c\u00f3 b\u1ed1n \u0111\u1ec9nh, b\u1ed1n c\u1ea1nh v\u00e0 b\u1ed1n g\u00f3c. Tuy nhi\u00ean, c\u00f3 nhi\u1ec1u \u0111\u1eb7c \u0111i\u1ec3m v\u00e0 lo\u1ea1i kh\u00e1c nhau c\u1ee7a h\u00ecnh t\u1ee9 gi\u00e1c, t\u1ea1o n\u00ean s\u1ef1 \u0111a d\u1ea1ng trong c\u00e1c c\u00f4ng th\u1ee9c to\u00e1n h\u1ecdc. C\u00e1c lo\u1ea1i h\u00ecnh t\u1ee9 gi\u00e1c ph\u1ed5 bi\u1ebfn bao g\u1ed3m h\u00ecnh vu\u00f4ng, h\u00ecnh ch\u1eef nh\u1eadt, h\u00ecnh thang v\u00e0 h\u00ecnh b\u00ecnh h\u00e0nh.\u00a0<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-1\"<\/picture><\/p>\n

Theo \u0111\u00f3, m\u1ed7i lo\u1ea1i h\u00ecnh t\u1ee9 gi\u00e1c mang theo nh\u1eefng thu\u1ed9c t\u00ednh ri\u00eang bi\u1ec7t v\u00e0 quy lu\u1eadt v\u1ec1 g\u00f3c, c\u1ea1nh c\u0169ng nh\u01b0 \u0111\u1ed1i x\u1ee9ng. \u0110\u1ed3ng th\u1eddi, \u0111\u1ed1i v\u1edbi h\u00ecnh t\u1ee9 gi\u00e1c n\u00e0o, t\u1ec9 l\u1ec7 c\u00e1c c\u1ea1nh v\u00e0 g\u00f3c c\u00f3 th\u1ec3 thay \u0111\u1ed5i, t\u1ea1o ra nh\u1eefng h\u00ecnh d\u1ea1ng v\u00e0 t\u00ednh ch\u1ea5t kh\u00e1c nhau. \u0110\u1eb7c bi\u1ec7t, trong to\u00e1n h\u1ecdc, h\u00ecnh t\u1ee9 gi\u00e1c th\u01b0\u1eddng \u0111\u01b0\u1ee3c nghi\u00ean c\u1ee9u s\u00e2u r\u1ed9ng trong l\u0129nh v\u1ef1c h\u00ecnh h\u1ecdc ph\u1eb3ng v\u00e0 kh\u00f4ng gian.\u00a0<\/span><\/p>\n

T\u1ea1i sao c\u00f4ng th\u1ee9c t\u00ednh chu vi h\u00ecnh t\u1ee9 gi\u00e1c l\u1ea1i quan tr\u1ecdng?<\/b><\/h2>\n

Chu vi l\u00e0 m\u1ed9t \u0111\u1ea1i l\u01b0\u1ee3ng \u0111o l\u01b0\u1eddng chi\u1ec1u d\u00e0i, v\u00e0 n\u00f3 gi\u00fap m\u00f4 t\u1ea3 k\u00edch th\u01b0\u1edbc t\u1ed5ng th\u1ec3 c\u1ee7a h\u00ecnh t\u1ee9 gi\u00e1c. \u0110i\u1ec1u n\u00e0y th\u1eadt s\u1ef1 h\u1eefu d\u1ee5ng khi ng\u01b0\u1eddi d\u00f9ng mu\u1ed1n hi\u1ec3u c\u0169ng nh\u01b0 t\u00ednh to\u00e1n c\u00e1c m\u00f4 h\u00ecnh trong kh\u00f4ng gian. B\u00ean c\u1ea1nh \u0111\u00f3, chu vi c\u00f2n gi\u00fap ph\u00e2n lo\u1ea1i c\u00e1c lo\u1ea1i h\u00ecnh t\u1ee9 gi\u00e1c v\u00e0 l\u00e0m n\u1ed5i b\u1eadt c\u00e1c \u0111\u1eb7c t\u00ednh \u0111\u1eb7c bi\u1ec7t c\u1ee7a ch\u00fang. T\u1eeb \u0111\u00f3, ch\u00fang ta c\u00f3 th\u1ec3 xem \u0111\u00e2y l\u00e0 m\u1ed9t c\u00f4ng c\u1ee5 c\u1ea7n thi\u1ebft \u0111\u1ec3 bi\u1ebft r\u00f5 h\u01a1n v\u1ec1 thu\u1ed9c t\u00ednh c\u1ee7a c\u00e1c d\u1ea1ng h\u00ecnh h\u1ecdc \u0111ang t\u1ed3n t\u1ea1i xung quanh ch\u00fang ta.<\/span><\/p>\n

H\u01a1n th\u1ebf n\u1eefa, c\u00f4ng th\u1ee9c t\u00ednh chu vi c\u1ee7a c\u00e1c h\u00ecnh t\u1ee9 gi\u00e1c kh\u00f4ng ch\u1ec9 \u0111\u01b0\u1ee3c \u00e1p d\u1ee5ng trong gi\u00e1o d\u1ee5c h\u1ecdc sinh. M\u00e0 \u1edf th\u1ef1c ti\u1ec5n, c\u00e1ch t\u00ednh chu vi \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng r\u1ed9ng r\u00e3i trong c\u00e1c l\u0129nh v\u1ef1c nh\u01b0 ki\u1ebfn tr\u00fac, x\u00e2y d\u1ef1ng v\u00e0 c\u00f4ng nghi\u1ec7p. \u0110\u1ec3 t\u1eeb \u0111\u00f3 gi\u00fap ng\u01b0\u1eddi d\u00f9ng c\u00f3 th\u1ec3 t\u00ednh to\u00e1n l\u01b0\u1ee3ng v\u1eadt li\u1ec7u c\u1ea7n thi\u1ebft ho\u1eb7c \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o \u0111\u1ed9 ch\u1eafc ch\u1eafn c\u1ee7a c\u00e1c k\u1ebft c\u1ea5u trong c\u00f4ng tr\u00ecnh.<\/span><\/p>\n

C\u00f4ng th\u1ee9c t\u00ednh chu vi h\u00ecnh t\u1ee9 gi\u00e1c nh\u01b0 th\u1ebf n\u00e0o?<\/b><\/h2>\n

\u1ede ph\u1ea7n kh\u00e1i ni\u1ec7m, ch\u00fang t\u00f4i c\u0169ng c\u00f3 nh\u1eafc \u0111\u1ebfn nhi\u1ec1u h\u00ecnh th\u1ee9c kh\u00e1c nhau c\u1ee7a h\u00ecnh t\u1ee9 gi\u00e1c. Tuy nhi\u00ean, nh\u1eb1m gi\u00fap cho b\u1ea1n \u0111\u1ecdc d\u1ec5 d\u00e0ng \u00e1p d\u1ee5ng c\u00f4ng th\u1ee9c h\u01a1n th\u00ec ch\u00fang t\u00f4i chia th\u00e0nh 2 lo\u1ea1i h\u00ecnh t\u1ee9 gi\u00e1c. D\u1ef1a v\u00e0o \u0111\u00e2y, ch\u00fang ta s\u1ebd c\u00f3 nh\u1eefng c\u00f4ng th\u1ee9c \u00e1p d\u1ee5ng ri\u00eang v\u00e0 m\u1eddi b\u1ea1n c\u00f9ng tham kh\u1ea3o th\u00eam nh\u00e9.<\/span><\/p>\n

T\u1ee9 gi\u00e1c b\u00ecnh th\u01b0\u1eddng<\/b><\/h3>\n

Ch\u00fang ta s\u1ebd c\u00f3 m\u1ed9t c\u00f4ng th\u1ee9c chung \u0111\u1ec3 t\u00ednh chu vi c\u1ee7a c\u00e1c h\u00ecnh t\u1ee9 gi\u00e1c gi\u1ea3n \u0111\u01a1n. C\u1ee5 th\u1ec3, b\u1ea1n s\u1ebd t\u00ednh chu vi b\u1eb1ng t\u1ed5ng chi\u1ec1u d\u00e0i c\u1ee7a c\u00e1c c\u1ea1nh t\u1ee9 gi\u00e1c. V\u00ed d\u1ee5 n\u1ebfu m\u1ed9t t\u1ee9 gi\u00e1c c\u00f3 4 c\u1ea1nh l\u00e0 a, b, c v\u00e0 d th\u00ec c\u00f4ng th\u1ee9c c\u1ee7a b\u1ea1n b\u1eb1ng (a + b + c + d).<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-2-3\"<\/picture><\/p>\n

Ng\u01b0\u1eddi d\u00f9ng c\u1ea7n l\u01b0u \u00fd r\u1eb1ng, c\u00f4ng th\u1ee9c n\u00e0y s\u1ebd \u00e1p d\u1ee5ng v\u1edbi h\u1ea7u h\u1ebft c\u00e1c h\u00ecnh t\u1ee9 gi\u00e1c, bao g\u1ed3m c\u1ea3 nh\u1eefng h\u00ecnh c\u00f3 hay kh\u00f4ng c\u00e1c c\u1ea1nh b\u1eb1ng nhau. Hay n\u00f3i theo h\u01b0\u1edbng kh\u00e1c, c\u00f4ng th\u1ee9c n\u00e0y c\u00f3 th\u1ec3 \u00e1p d\u1ee5ng v\u1edbi c\u1ea3 h\u00ecnh ch\u1eef nh\u1eadt, h\u00ecnh vu\u00f4ng v\u00e0 c\u00e1c h\u00ecnh c\u00f3 b\u1ed1n c\u1ea1nh kh\u00e1c. V\u00e0 ng\u01b0\u1eddi d\u00f9ng ch\u1ec9 c\u1ea7n bi\u1ebft \u0111\u1ebfn \u0111\u1ed9 d\u00e0i c\u1ee7a b\u1ed1n c\u1ea1nh l\u00e0 c\u00f3 th\u1ec3 \u00e1p d\u1ee5ng c\u00f4ng th\u1ee9c th\u00e0nh c\u00f4ng r\u1ed3i nh\u00e9.<\/span><\/p>\n

T\u1ee9 gi\u00e1c c\u00f3 \u0111i\u1ec1u ki\u1ec7n<\/b><\/h3>\n

\u0110\u00fang theo t\u00ean g\u1ecdi, t\u1ee9 gi\u00e1c c\u00f3 \u0111i\u1ec1u ki\u1ec7n s\u1ebd \u0111\u01b0\u1ee3c t\u1ea1o th\u00e0nh khi ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t s\u1ed1 ti\u00eau ch\u00ed nh\u1ea5t \u0111\u1ecbnh. Ch\u1eb3ng h\u1ea1n nh\u01b0 ch\u00fang ta s\u1ebd c\u00f3 m\u1ed9t s\u1ed1 m\u00f4 h\u00ecnh t\u1ee9 gi\u00e1c vu\u00f4ng, t\u1ee9 gi\u00e1c c\u00e2n, t\u1ee9 gi\u00e1c l\u1ed3i hay t\u1ee9 gi\u00e1c l\u00f5m. V\u00e0 t\u00f9y thu\u1ed9c v\u00e0o t\u00ednh ch\u1ea5t c\u1ee7a m\u1ed7i h\u00ecnh m\u00e0 ch\u00fang ta s\u1ebd \u00e1p d\u1ee5ng c\u00e1c c\u00f4ng th\u1ee9c \u0111a d\u1ea1ng nh\u01b0 sau \u0111\u00e2y.<\/span><\/p>\n

C\u00f4ng th\u1ee9c 1: <\/span>Chu vi h\u00ecnh t\u1ee9 gi\u00e1c<\/b> theo d\u1ea1ng b\u00ecnh h\u00e0nh: Chu vi (P) = 2 x (\u0110\u1ed9 d\u00e0i c\u1ea1nh \u0111\u00e1y + \u0110\u1ed9 d\u00e0i c\u1ea1nh b\u00ean).<\/span><\/p>\n

C\u00f4ng th\u1ee9c 2: Chu vi h\u00ecnh \u0111\u1ec1u (h\u00ecnh t\u1ee9 gi\u00e1c c\u00f3 c\u1ea3 b\u1ed1n c\u1ea1nh b\u1eb1ng nhau): Chu vi (P) = 4 x \u0110\u1ed9 d\u00e0i c\u1ea1nh (a).<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-4\"<\/picture><\/p>\n

C\u00f4ng th\u1ee9c 3: Chu vi h\u00ecnh vu\u00f4ng: Chu vi (P) = 4 x \u0110\u1ed9 d\u00e0i c\u1ea1nh (a).<\/span><\/p>\n

C\u00f4ng th\u1ee9c 4: Chu vi h\u00ecnh ch\u1eef nh\u1eadt: Chu vi (P) = 2 x (Chi\u1ec1u d\u00e0i + Chi\u1ec1u r\u1ed9ng) ho\u1eb7c\u00a0 P = 2a + 2b (n\u1ebfu a v\u00e0 b l\u00e0 chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng).<\/span><\/p>\n

T\u1ed5ng h\u1ee3p c\u00e1c d\u1ea1ng b\u00e0i t\u1eadp t\u00ednh chu vi h\u00ecnh t\u1ee9 gi\u00e1c, c\u00f3 b\u00e0i gi\u1ea3i<\/b><\/h2>\n

\u201cH\u1ecdc ph\u1ea3i \u0111i \u0111\u00f4i v\u1edbi h\u00e0nh\u201d, khi ch\u00fang ta \u0111\u00e3 bi\u1ebft \u0111\u01b0\u1ee3c t\u1ea5t c\u1ea3 c\u00f4ng th\u1ee9c th\u00ec nhi\u1ec7m v\u1ee5 ti\u1ebfp theo c\u1ee7a b\u1ea1n l\u00e0 ph\u1ea3i \u00e1p d\u1ee5ng \u0111\u01b0\u1ee3c n\u00f3 v\u00e0o th\u1ef1c ti\u1ec5n. Hi\u1ec3u \u0111\u01b0\u1ee3c v\u1ea5n \u0111\u1ec1 quan tr\u1ecdng n\u00e0y n\u00ean ngay trong \u0111\u00e2y Ho\u00e0ng H\u00e0 Mobile \u0111\u00e3 t\u1ed5ng h\u1ee3p cho b\u1ea1n c\u00e1c d\u1ea1ng b\u00e0i t\u1eadp t\u00ednh chu vi h\u00ecnh h\u1ecdc r\u1ea5t th\u00fa v\u1ecb. N\u1ebfu b\u1ea1n b\u1ecf l\u1ee1 qua th\u00ec ch\u1eafc ch\u1eafn s\u1ebd thi\u1ebfu s\u00f3t r\u1ea5t l\u1edbn \u0111\u1ea5y nh\u00e9.<\/span><\/p>\n

D\u1ea1ng 1: T\u00ednh chu vi khi \u0111\u00e3 bi\u1ebft \u0111\u01b0\u1ee3c \u0111\u1ed9 d\u00e0i c\u1ee7a c\u00e1c c\u1ea1nh<\/b><\/h3>\n

\u0110\u1ea7u ti\u00ean ch\u00fang ta s\u1ebd c\u00f9ng nhau t\u00ecm hi\u1ec3u d\u1ea1ng b\u00e0i t\u1eadp c\u01a1 b\u1ea3n nh\u1ea5t trong c\u00e1ch t\u00ednh chu vi h\u00ecnh h\u1ecdc. C\u1ee5 th\u1ec3, ch\u00fang ta s\u1ebd c\u00f3 t\u1ea5t c\u1ea3 nh\u1eefng d\u1eef ki\u1ec7n v\u1ec1 \u0111\u1ed9 d\u00e0i c\u00e1c c\u1ea1nh c\u1ee7a h\u00ecnh t\u1ee9 gi\u00e1c. V\u1eady n\u00ean ch\u00fang ta ch\u1ec9 c\u1ea7n \u00e1p d\u1ee5ng c\u00f4ng th\u1ee9c P = a + b + c + d l\u00e0 c\u00f3 th\u1ec3 ho\u00e0n th\u00e0nh \u0111\u01b0\u1ee3c th\u1eed th\u00e1ch \u0111\u1ea7u ti\u00ean r\u1ed3i n\u00e8.<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-5\"<\/picture><\/p>\n

V\u00ed d\u1ee5: Ch\u00fang ta c\u00f3 \u0111\u01b0\u1ee3c \u0111\u1ed9 d\u00e0i b\u1ed1n c\u1ea1nh, a = 2cm, b = 4cm, c = 6cm v\u00e0 d = 8cm. D\u1ef1a v\u00e0o c\u00f4ng th\u1ee9c t\u00ednh <\/span>chu vi h\u00ecnh t\u1ee9 gi\u00e1c<\/b>, ta c\u00f3: P =\u00a0 2 + 4 + 6 + 8 = 20cm.<\/span><\/p>\n

D\u1ea1ng 2: C\u00f3 chu vi, t\u00ednh ng\u01b0\u1ee3c l\u1ea1i \u0111\u1ed9 d\u00e0i c\u00e1c c\u1ea1nh<\/b><\/h3>\n

Thay v\u00ec ch\u00fang ta t\u00ednh to\u00e1n theo c\u00f4ng th\u1ee9c thu\u1eadn chi\u1ec1u, v\u1edbi d\u1ea1ng n\u00e0y ch\u00fang ta s\u1ebd \u0111i ng\u01b0\u1ee3c l\u1ea1i m\u1ed9t ch\u00fat. T\u1ea1i \u0111\u00e2y, b\u1ea1n s\u1ebd bi\u1ebft \u0111\u01b0\u1ee3c chu vi c\u1ee7a h\u00ecnh t\u1ee9 gi\u00e1c v\u00e0 y\u00eau c\u1ea7u ph\u1ea3i t\u00ednh \u0111\u01b0\u1ee3c \u0111\u1ed9 d\u00e0i c\u1ea1nh. V\u00e0 t\u01b0\u01a1ng t\u1ef1 ch\u00fang ta s\u1ebd ti\u1ebfp t\u1ee5c v\u1eadn d\u1ee5ng c\u00f4ng th\u1ee9c P = a + b + c + d \u1edf d\u1ea1ng b\u00e0i to\u00e1n n\u00e0y nh\u00e9.<\/span><\/p>\n

V\u00ed d\u1ee5: Ch\u00fang ta c\u00f3 chu vi h\u00ecnh ABCD = AB + BC + CD + DA = 52cm. \u0110\u1ed3ng th\u1eddi, ch\u00fang ta c\u0169ng bi\u1ebft \u0111\u01b0\u1ee3c \u0111\u1ed9 d\u00e0i hai c\u1ea1nh AB + BC = 21cm. Y\u00eau c\u1ea7u \u0111\u1eb7t ra l\u00e0 b\u1ea1n ph\u1ea3i t\u00ednh \u0111\u01b0\u1ee3c t\u1ed5ng \u0111\u1ed9 d\u00e0i c\u1ee7a hai c\u1ea1nh CD + DA.<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-6\"<\/picture><\/p>\n

B\u00e0i gi\u1ea3i: AB + BC = 2P = 21 + (CD + DA) = 45cm. V\u1eady \u0111\u1ec3 gi\u1ea3i \u0111\u01b0\u1ee3c b\u00e0i to\u00e1n n\u00e0y ch\u00fang ta s\u1ebd th\u1ef1c hi\u1ec7n nh\u01b0 th\u1ebf n\u00e0o? Tr\u01b0\u1edbc ti\u00ean b\u1ea1n c\u1ea7n \u00e1p d\u1ee5ng c\u00f4ng th\u1ee9c v\u00e0 ch\u00fang ta s\u1ebd c\u00f3 \u0111\u01b0\u1ee3c t\u1ed5ng \u0111\u1ed9 d\u00e0i c\u1ee7a c\u00e1c c\u1ea1nh CD + DA = 52 – 21 = 31cm. V\u1eady l\u00e0 k\u1ebft qu\u1ea3 cu\u1ed1i c\u00f9ng c\u1ee7a b\u00e0i to\u00e0n l\u00e0 31cm.<\/span><\/p>\n

D\u1ea1ng 3: C\u00f4ng th\u1ee9c t\u00ednh chu vi h\u00ecnh t\u1ee9 gi\u00e1c \u0111\u1eb7c bi\u1ec7t<\/b><\/h3>\n

Nh\u01b0 \u0111\u00e3 bi\u1ebft, ch\u00fang ta s\u1ebd c\u00f3 h\u00ecnh t\u1ee9 gi\u00e1c \u0111\u1eb7c bi\u1ec7t \u0111\u01b0\u1ee3c t\u1ea1o th\u00e0nh t\u1eeb nh\u1eefng \u0111i\u1ec1u ki\u1ec7n nh\u1ea5t \u0111\u1ecbnh. \u0110\u1ed3ng th\u1eddi, Ho\u00e0ng H\u00e0 Mobile c\u0169ng \u0111\u00e3 cung c\u1ea5p c\u00f4ng th\u1ee9c chi ti\u1ebft cho b\u1ea1n. Do \u0111\u00f3, \u1edf d\u1ea1ng b\u00e0i t\u1eadp n\u00e0y ch\u00fang ta s\u1ebd \u0111\u01b0\u1ee3c cho m\u1ed9t h\u00ecnh vu\u00f4ng ho\u1eb7c h\u00ecnh ch\u1eef nh\u1eadt v\u1edbi c\u00e1c d\u1eef ki\u1ec7n v\u1ec1 c\u1ea1nh v\u00e0 y\u00eau c\u1ea7u t\u00ednh chu vi.\u00a0<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-7\"<\/picture><\/p>\n

V\u00ed d\u1ee5: M\u1ea3nh \u0111\u1ea5t nh\u00e0 b\u1ea1n h\u00ecnh ch\u1eef nh\u1eadt v\u1edbi chi\u1ec1u d\u00e0i l\u00e0 20m v\u00e0 chi\u1ec1u r\u1ed9ng l\u00e0 8m. \u0110\u1ec1 b\u00e0i y\u00eau c\u1ea7u b\u1ea1n ph\u1ea3i t\u00ednh \u0111\u01b0\u1ee3c chu vi c\u1ee7a m\u1ea3nh \u0111\u1ea5t tr\u00ean. T\u1eeb d\u1eef ki\u1ec7n n\u00e0y, ch\u00fang ta s\u1ebd d\u00f9ng c\u00f4ng th\u1ee9c Chu vi (P) = 2 x (Chi\u1ec1u d\u00e0i + Chi\u1ec1u r\u1ed9ng) =\u00a0 2 x (20 + 8) = 56m.<\/span><\/p>\n

B\u00e0i luy\u1ec7n t\u1eadp c\u00e1ch t\u00ednh chu vi t\u1ee9 gi\u00e1c d\u00e0nh cho b\u00e9 l\u1edbp 3, l\u1edbp 4<\/b><\/h2>\n

B\u00ean c\u1ea1nh vi\u1ec7c cung c\u1ea5p cho th\u00f4ng tin v\u1ec1 c\u00e1c d\u1ea1ng b\u00e0i t\u1eadp ph\u1ed5 bi\u1ebfn nh\u1ea5t c\u1ee7a h\u00ecnh t\u1ee9 gi\u00e1c. Ho\u00e0ng H\u00e0 Mobile s\u1ebd g\u1ee3i \u00fd th\u00eam m\u1ed9t v\u00e0i b\u00e0i luy\u1ec7n t\u1eadp \u0111\u1ec3 n\u00e2ng cao kh\u1ea3 n\u0103ng t\u00ednh to\u00e1n c\u1ee7a c\u00e1c b\u1ea1n nh\u1ecf. \u0110\u1eb7c bi\u1ec7t b\u00e0i t\u1eadp n\u00e0y s\u1ebd chuy\u00ean d\u00e0nh cho c\u00e1c b\u00e9 l\u1edbp 3 v\u00e0 l\u1edbp 4, n\u00ean ba m\u1eb9 c\u00f3 th\u1ec3 t\u00ecm hi\u1ec3u v\u00e0 c\u00f9ng b\u00e9 gi\u1ea3i to\u00e1n t\u1ea1i nh\u00e0 nh\u00e9.<\/span><\/p>\n

B\u00e0i t\u1eadp 1<\/b><\/h3>\n

B\u00e1c H\u1ea3i mu\u1ed1n l\u00e1t g\u1ea1ch cho n\u1ec1n ph\u00f2ng ng\u1ee7 v\u1edbi chi\u1ec1u d\u00e0i l\u00e0 4m v\u00e0 chi\u1ec1u ngang l\u00e0 3m. Trong \u0111\u00f3, lo\u1ea1i g\u1ea1ch l\u00e1t m\u00e0 b\u00e1c s\u1eed d\u1ee5ng c\u00f3 h\u00ecnh vu\u00f4ng v\u1edbi c\u1ea1nh l\u00e0 60cm. H\u1ecfi b\u00e1c H\u1ea3i ph\u1ea3i mua bao nhi\u00eau vi\u00ean g\u1ea1ch \u0111\u1ec3 x\u00e2y d\u1ef1ng ho\u00e0n t\u1ea5t cho c\u0103n ph\u00f2ng ng\u1ee7.<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-8\"<\/picture><\/p>\n

L\u1eddi gi\u1ea3i: Ch\u00fang ta c\u00f3 di\u1ec7n t\u00edch c\u0103n ph\u00f2ng b\u1eb1ng 4 x 3 = 18m2 = 120.000cm2. Trong \u0111\u00f3, m\u1ed9t vu\u00f4ng g\u1ea1ch s\u1ebd c\u00f3 di\u1ec7n t\u00edch b\u1eb1ng 60 x 60 = 1.200cm2. V\u1eady ch\u00fang ta s\u1ebd c\u00f3 t\u1ed5ng s\u1ed1 vi\u00ean g\u1ea1ch m\u00e0 b\u00e1c H\u1ea3i c\u1ea7n s\u1eed d\u1ee5ng l\u00e0 120.000 : 1.200 = 100 vi\u00ean.<\/span><\/p>\n

B\u00e0i t\u1eadp 2<\/b><\/h3>\n

M\u1ed9t h\u00ecnh thoi ABCD c\u00f3 \u0111\u1ed9 d\u00e0i hai \u0111\u01b0\u1eddng ch\u00e9o l\u1ea7n l\u01b0\u1ee3t l\u00e0 5m v\u00e0 4m. V\u00e2y di\u1ec7n t\u00edch h\u00ecnh thoi ABCD b\u1eb1ng bao nhi\u00eau?<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-9\"<\/picture><\/p>\n

L\u1eddi gi\u1ea3i: \u0110\u1ec3 t\u00ednh \u0111\u01b0\u1ee3c b\u00e0i to\u00e1n n\u00e0y ph\u1ea3i n\u00f3i l\u00e0 c\u1ef1c k\u1ef3 \u0111\u01a1n gi\u1ea3n, ch\u00fang ta s\u1ebd t\u00ednh di\u1ec7n t\u00edch h\u00ecnh thoi ABCD = (5 x 4)\/2 = 10m2. V\u00e0 k\u1ebft qu\u1ea3 cu\u1ed1i c\u00f9ng ch\u00fang ta thu \u0111\u01b0\u1ee3c v\u1ec1 di\u1ec7n t\u00edch c\u1ee7a h\u00ecnh th\u00f4i ABCD l\u00e0 10m2.<\/span><\/p>\n

B\u00e0i t\u1eadp 3<\/b><\/h3>\n

M\u1ed9t khu v\u01b0\u1eddn tr\u1ed3ng hoa h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chi\u1ec1u d\u00e0i (a = 15cm) v\u00e0 chi\u1ec1u r\u1ed9ng (b = 10cm). Trong khi \u0111\u00f3, c\u1ed5ng c\u00f3 chi\u1ec1u r\u1ed9ng b\u1eb1ng \u2153 chi\u1ec1u d\u00e0i v\u00e0 ph\u1ea7n c\u00f2n l\u1ea1i l\u00e0 h\u00e0ng r\u00e0o. C\u00e2u h\u1ecfi \u0111\u1eb7t ra l\u00e0 h\u00e0ng r\u00e0o c\u1ee7a khu v\u01b0\u1eddn tr\u1ed3ng hoa d\u00e0i bao nhi\u00eau m\u00e9t?<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-10\"<\/picture><\/p>\n

L\u1eddi gi\u1ea3i: Tr\u01b0\u1edbc ti\u00ean, ch\u00fang ta c\u1ea7n ph\u1ea3i t\u00ednh \u0111\u01b0\u1ee3c \u0111\u1ed9 r\u1ed9ng c\u1ee7a c\u1ed5ng = 15\/3 = 5cm. Ti\u1ebfp \u0111\u1ebfn, b\u1ea1n s\u1ebd t\u00ednh <\/span>chu vi h\u00ecnh t\u1ee9 gi\u00e1c <\/b>(h\u00ecnh ch\u1eef nh\u1eadt) = 2.(10 + 15) = 2.25 = 50m. V\u1eady ch\u00fang ta c\u00f3 th\u1ec3 k\u1ebft lu\u1eadn r\u1eb1ng chi\u1ec1u d\u00e0i c\u1ee7a h\u00e0ng r\u00e0o khu v\u01b0\u1eddn tr\u1ed3ng hoa b\u1eb1ng 50 \u2013 5 = 45m.<\/span><\/p>\n

T\u1ea1i sao chu vi t\u1ee9 gi\u00e1c s\u1ebd ph\u1ee5 thu\u1ed9c nhi\u1ec1u v\u00e0o c\u00e1c \u0111\u01b0\u1eddng ch\u00e9o?<\/b><\/h2>\n

Theo th\u00f4ng tin ch\u00fang t\u00f4i t\u00ecm hi\u1ec3u \u0111\u01b0\u1ee3c th\u00ec c\u00f3 r\u1ea5t nhi\u1ec1u b\u1ea1n th\u1eafc m\u1eafc r\u1eb1ng \u201cT\u1ea1i sao h\u00ecnh t\u1ee9 gi\u00e1c c\u00f3 th\u1ec3 kh\u00e1c nhau \u0111\u1ed1i v\u1edbi 2 \u0111\u01b0\u1eddng ch\u00e9o kh\u00e1c nhau?\u201d. \u0110\u1ea7u ti\u00ean, b\u1ea1n \u0111\u1ecdc c\u1ea7n bi\u1ebft r\u00f5 v\u1ec1 c\u1ea5u tr\u00fac c\u1ee7a hai \u0111\u01b0\u1eddng ch\u00e9o trong h\u00ecnh h\u1ecdc t\u1ee9 gi\u00e1c, \u0111\u00f3 ch\u00ednh l\u00e0 2 \u0111\u01b0\u1eddng \u0111\u01b0\u1ee3c t\u1ea1o th\u00e0nh khi n\u1ed1i c\u00e1c \u0111i\u1ec3m \u0111\u1ed1i x\u1ee9ng, kh\u00f4ng li\u1ec1n k\u1ec1. Song song \u0111\u00f3, khi ch\u00fang ta t\u00ednh chu vi c\u1ee7a h\u00ecnh t\u1ee9 gi\u00e1c th\u00ec b\u1eaft bu\u1ed9c ph\u1ea3i t\u00ednh \u0111\u01b0\u1ee3c t\u1ed5ng c\u1ee7a c\u00e1c c\u1ea1nh trong h\u00ecnh.<\/span><\/p>\n

\"chu-vi-hinh-tu-giac-11\"<\/picture><\/p>\n

Ch\u00ednh v\u00ec v\u1eady m\u00e0, m\u1ed9t khi c\u00e1c \u0111\u01b0\u1eddng ch\u00e9o thay \u0111\u1ed5i th\u00ec chi\u1ec1u d\u00e0i c\u1ee7a c\u00e1c c\u1ea1nh c\u0169ng thay \u0111\u1ed5i t\u01b0\u01a1ng x\u1ee9ng. K\u00e9o theo \u0111\u00f3 l\u00e0 t\u1ed5ng c\u1ee7a c\u00e1c c\u1ea1nh c\u0169ng thay \u0111\u1ed5i v\u00e0 t\u1ea1o ra m\u1ed9t h\u00ecnh t\u1ee9 gi\u00e1c c\u00f3 nhi\u1ec1u bi\u1ebfn th\u1ec3 kh\u00e1c nhau. V\u00ed d\u1ee5 ch\u00fang ta ch\u1ecdn m\u1ed9t \u0111\u01b0\u1eddng ch\u00e9o ng\u1eafn h\u01a1n th\u00ec t\u1ed5ng chi\u1ec1u d\u00e0i c\u1ee7a c\u00e1c c\u1ea1nh s\u1ebd gi\u1ea3m xu\u1ed1ng. V\u00e0 k\u1ebft qu\u1ea3 l\u00e0 chu vi c\u1ee7a t\u1ee9 gi\u00e1c s\u1ebd nh\u1ecf h\u01a1n so v\u1edbi vi\u1ec7c s\u1eed d\u1ee5ng \u0111\u01b0\u1eddng ch\u00e9o d\u00e0i h\u01a1n.<\/span><\/p>\n

Tuy nhi\u00ean c\u00f3 m\u1ed9t l\u01b0u \u00fd h\u1ebft s\u1ee9c quan tr\u1ecdng m\u00e0 b\u1ea1n c\u1ea7n n\u1eafm r\u00f5, \u0111\u00f3 ch\u00ednh l\u00e0 k\u00edch th\u01b0\u1edbc c\u1ee7a \u0111\u01b0\u1eddng ch\u00e9o c\u0169ng c\u00f3 th\u1ec3 ph\u1ee5 thu\u1ed9c v\u00e0o lo\u1ea1i t\u1ee9 gi\u00e1c v\u00e0 c\u00e1c \u0111\u1ec9nh c\u1ee7a n\u00f3. Ch\u00ednh v\u00ec th\u1ebf, khi t\u00ednh chu vi t\u1ee9 gi\u00e1c d\u1ef1a v\u00e0o c\u00e1c \u0111\u01b0\u1eddng ch\u00e9o th\u00ec b\u1ea1n c\u1ea7n ph\u1ea3i x\u00e1c \u0111\u1ecbnh ch\u00ednh x\u00e1c \u0111\u1ed9 d\u00e0i c\u1ee7a n\u00f3 \u0111\u1ec3 c\u00f3 \u0111\u01b0\u1ee3c k\u1ebft qu\u1ea3 \u0111\u00fang nh\u1ea5t.<\/span><\/p>\n

K\u1ebft lu\u1eadn<\/b><\/h2>\n

Nh\u01b0 v\u1eady, ch\u00fang ta \u0111\u00e3 t\u00ecm hi\u1ec3u v\u1ec1 <\/span>c\u00e1ch t\u00ednh chu vi h\u00ecnh t\u1ee9 gi\u00e1c l\u00e0 g\u00ec<\/b>. \u0110\u1ed3ng th\u1eddi, b\u1ea1n \u0111\u1ecdc c\u0169ng bi\u1ebft c\u00e1ch v\u1eadn d\u1ee5ng c\u00f4ng th\u1ee9c v\u00e0o c\u00e1c b\u00e0i to\u00e1n th\u1ef1c t\u1ebf. Ri\u00eang \u0111\u1ed1i v\u1edbi c\u00e1c b\u1ea1n nh\u1ecf c\u1ea7n ph\u1ea3i n\u1eafm ch\u1eafc c\u00e1c ki\u1ebfn th\u1ee9c c\u01a1 b\u1ea3n n\u00e0y \u0111\u1ec3 b\u1ed5 tr\u1ee3 cho ph\u1ea7n t\u00ednh to\u00e1n h\u00ecnh h\u1ecdc \u1edf c\u00e1c l\u1edbp tr\u00ean.<\/span><\/p>\n

Xem th\u00eam:<\/b><\/p>\n