H\u00ecnh ch\u1eef nh\u1eadt l\u00e0 t\u1ee9 gi\u00e1c c\u00f3 b\u1ed1n g\u00f3c vu\u00f4ng, 2 c\u1ea1nh d\u00e0i b\u1eb1ng nhau v\u00e0 2 c\u1ea1nh ng\u1eafn b\u1eb1ng nhau.<\/p>\n
- \n
- T\u00ednh ch\u1ea5t c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt.<\/li>\n<\/ol>\n
– Chu vi h\u00ecnh ch\u1eef nh\u1eadt l\u00e0 1 s\u1ed1 chia h\u1ebft cho 2 n\u1ebfu chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt \u0111\u00f3 l\u00e0 c\u00e1c s\u1ed1 t\u1ef1 nhi\u00ean.<\/p>\n
– N\u1ebfu t\u0103ng chi\u1ec1u d\u00e0i c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt l\u00ean a \u0111\u01a1n v\u1ecb th\u00ec chu vi h\u00ecnh ch\u1eef nh\u1eadt \u0111\u00f3 t\u0103ng l\u00ean a x 2 \u0111\u01a1n v\u1ecb.<\/p>\n
– N\u1ebfu t\u0103ng chi\u1ec1u r\u1ed9ng c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt l\u00ean a \u0111\u01a1n v\u1ecb th\u00ec chu vi h\u00ecnh ch\u1eef nh\u1eadt \u0111\u00f3 t\u0103ng l\u00ean a x 2 \u0111\u01a1n v\u1ecb.<\/p>\n
– N\u1ebfu gi\u1ea3m chi\u1ec1u d\u00e0i c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt \u0111i a \u0111\u01a1n v\u1ecb th\u00ec chu vi h\u00ecnh ch\u1eef nh\u1eadt \u0111\u00f3 gi\u1ea3m \u0111i a x 2 \u0111\u01a1n v\u1ecb.<\/p>\n
– N\u1ebfu gi\u1ea3m chi\u1ec1u r\u1ed9ng c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt \u0111i a \u0111\u01a1n v\u1ecb th\u00ec chu vi h\u00ecnh ch\u1eef nh\u1eadt \u0111\u00f3 gi\u1ea3m \u0111i a x 2 \u0111\u01a1n v\u1ecb.<\/p>\n
– N\u1ebfu g\u1ea5p chi\u1ec1u d\u00e0i ho\u1eb7c chi\u1ec1u r\u1ed9ng c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt\u00a0 l\u00ean bao nhi\u00eau l\u1ea7n th\u00ec di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt \u0111\u00f3 s\u1ebd t\u0103ng l\u00ean b\u1ea5y nhi\u00eau l\u1ea7n v\u00e0 ng\u01b0\u1ee3c l\u1ea1i.<\/p>\n
- \n
- C\u00f4ng th\u1ee9c t\u00ednh chu vi h\u00ecnh ch\u1eef nh\u1eadt:<\/li>\n<\/ol>\n
![\"\"](\"https:\/\/onthitot.com\/wp-content\/uploads\/2018\/01\/cong-thuc-tinh-chu-vi-hinh-chu-nhat-300x167.png\")
H\u00ecnh ch\u1eef nh\u1eadt v\u00e0 c\u00f4ng th\u1ee9c t\u00ednh chu vi h\u00ecnh ch\u1eef nh\u1eadt<\/figcaption><\/figure>\n Chu vi h\u00ecnh ch\u1eef nh\u1eadt b\u1eb1ng 2 l\u1ea7n t\u1ed5ng c\u1ee7a chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng<\/p>\n
C = 2 x (a+b)<\/p>\n
- \n
- C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt:<\/li>\n<\/ol>\n
![\"\"](\"https:\/\/onthitot.com\/wp-content\/uploads\/2018\/01\/cong-thuc-tinh-dien-tich-hinh-chu-nhat-300x167.png\")
H\u00ecnh ch\u1eef nh\u1eadt v\u00e0 c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt<\/figcaption><\/figure>\n Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt b\u1eb1ng t\u00edch chi\u1ec1u d\u00e0i nh\u00e2n chi\u1ec1u r\u1ed9ng.<\/p>\n
S = a x b<\/p>\n
B\u00e0i t\u1eadp v\u1eadn d\u1ee5ng v\u1ec1 c\u00e1c c\u00f4ng th\u1ee9c t\u00ednh chu vi h\u00ecnh ch\u1eef nh\u1eadt, di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt<\/strong><\/p>\n
B\u00e0i 1:<\/strong> Cho h\u00ecnh ch\u1eef nh\u1eadt ABCD, c\u00f3 chi\u1ec1u d\u00e0i AB = 7cm, chi\u1ec1u r\u1ed9ng AD = 5cm. T\u00ednh di\u1ec7n t\u00edch v\u00e0 chu vi h\u00ecnh ch\u1eef nh\u1eadt.<\/p>\n
L\u1eddi gi\u1ea3i<\/u><\/em><\/p>\n
![\"\"](\"https:\/\/onthitot.com\/wp-content\/uploads\/2018\/01\/vi-du-cong-thuc-tinh-chu-vi-hinh-chu-nhat-va-dien-tich-hinh-chu-nhat-300x167.png\")
<\/p>\nChu vi h\u00ecnh ch\u1eef nh\u1eadt b\u1eb1ng :<\/p>\n
C = 2 x (a+b) = 2 x (7+5) = 24 (cm)<\/p>\n
Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt b\u1eb1ng:<\/p>\n
S = a x b = 7 x 5 =35 (cm2<\/sup>)<\/p>\n
\u0110\u00e1p s\u1ed1: C = 24 cm, S = 35 cm<\/p>\n
B\u00e0i 2<\/strong>: T\u00ecm chu vi c\u1ee7a 1 h\u00ecnh ch\u1eef nh\u1eadt bi\u1ebft chi\u1ec1u r\u1ed9ng b\u1eb1ng 5m, v\u00e0 c\u00f3 di\u1ec7n t\u00edch b\u1eb1ng 60 m2<\/sup>.<\/p>\n
L\u1eddi gi\u1ea3i<\/u><\/em><\/p>\n
Chi\u1ec1u d\u00e0i c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt b\u1eb1ng:<\/p>\n
60 : 5 = 12 (cm)<\/p>\n
Chu vi h\u00ecnh ch\u1eef nh\u1eadt b\u1eb1ng:<\/p>\n
2 x (12 + 5 ) = 34(cm)<\/p>\n
\u0110\u00e1p s\u1ed1: C = 34 cm<\/p>\n
B\u00e0i 3:<\/strong> M\u1ed9t mi\u1ebfng b\u00eca h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chu vi 96 cm, n\u1ebfu gi\u1ea3m chi\u1ec1u d\u00e0i 13 cm v\u00e0 gi\u1ea3m chi\u1ec1u r\u1ed9ng 5 cm th\u00ec \u0111\u01b0\u1ee3c m\u1ed9t h\u00ecnh vu\u00f4ng. H\u1ecfi mi\u1ebfng b\u00eca h\u00ecnh ch\u1eef nh\u1eadt \u0111\u00f3 c\u00f3 di\u1ec7n t\u00edch b\u1eb1ng bao nhi\u00eau?<\/p>\n
L\u1eddi gi\u1ea3i:<\/u><\/em><\/p>\n
Mi\u1ebfng b\u00eca h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chi\u1ec1u d\u00e0i h\u01a1n chi\u1ec1u r\u1ed9ng l\u00e0:<\/p>\n
13 \u2013 5 = 8 (cm)<\/p>\n
N\u1eeda chu vi h\u00ecnh ch\u1eef nh\u1eadt:<\/p>\n
96 : 2 = 48 (cm)<\/p>\n
Chi\u1ec1u r\u1ed9ng h\u00ecnh ch\u1eef nh\u1eadt l\u00e0:<\/p>\n
(48 \u2013 8) : 2 = 20 (cm)<\/p>\n
Chi\u1ec1u d\u00e0i h\u00ecnh ch\u1eef nh\u1eadt l\u00e0:<\/p>\n
20 + 8 = 28 (cm)<\/p>\n
Di\u1ec7n t\u00edch mi\u1ebfng b\u00eca h\u00ecnh ch\u1eef nh\u1eadt l\u00e0:<\/p>\n
28 x 20 = 560 (cm2<\/sup>)<\/p>\n
\u0110\u00e1p s\u1ed1: S = 560 (cm2<\/sup>)<\/p>\n
B\u00e0i 4:<\/strong> T\u00ecm di\u1ec7n t\u00edch c\u1ee7a m\u1ed9t h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chi\u1ec1u r\u1ed9ng 26 cm v\u00e0 c\u00f3 chu vi g\u1ea5p 3 l\u1ea7n chi\u1ec1u d\u00e0i?<\/p>\n
L\u1eddi gi\u1ea3i:<\/u><\/em><\/p>\n
Ta c\u00f3:<\/p>\n
Chu vi = chi\u1ec1u d\u00e0i x 3 = chi\u1ec1u d\u00e0i x 2 + chi\u1ec1u d\u00e0i.<\/p>\n
L\u1ea1i c\u00f3:<\/p>\n
Chu vi = chi\u1ec1u d\u00e0i x 2 + chi\u1ec1u r\u1ed9ng x 2<\/p>\n
V\u1eady: Chi\u1ec1u d\u00e0i = chi\u1ec1u r\u1ed9ng x 2.<\/p>\n
Chi\u1ec1u d\u00e0i h\u00ecnh ch\u1eef nh\u1eadt l\u00e0:<\/p>\n
26 x 2 = 52 (cm)<\/p>\n
Di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt l\u00e0:<\/p>\n
52 x 26 = 1352 (cm2<\/sup>)<\/p>\n
\u0110\u00e1p s\u1ed1: S = 1352 (cm2<\/sup>)<\/p>\n
B\u00e0i 5:<\/strong> M\u1ed9t mi\u1ebfng \u0111\u1ea5t h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chi\u1ec1u d\u00e0i 64 m, chi\u1ec1u r\u1ed9ng 34 m. Ng\u01b0\u1eddi ta gi\u1ea3m chi\u1ec1u d\u00e0i v\u00e0 t\u0103ng chi\u1ec1u r\u1ed9ng \u0111\u1ec3 mi\u1ebfng \u0111\u1ea5t l\u00e0 h\u00ecnh vu\u00f4ng, bi\u1ebft ph\u1ea7n di\u1ec7n t\u00edch gi\u1ea3m theo chi\u1ec1u d\u00e0i l\u00e0 272. T\u00ecm ph\u1ea7n di\u1ec7n t\u00edch t\u0103ng th\u00eam theo chi\u1ec1u r\u1ed9ng.<\/p>\n
L\u1eddi gi\u1ea3i:<\/u><\/em><\/p>\n
S\u1ed1 \u0111o b\u1ecb gi\u1ea3m c\u1ee7a chi\u1ec1u d\u00e0i mi\u1ebfng \u0111\u1ea5t l\u00e0:<\/p>\n
272 : 34 = 8 (m)<\/p>\n
C\u1ea1nh c\u1ee7a mi\u1ebfng \u0111\u1ea5t h\u00ecnh vu\u00f4ng l\u00e0:<\/p>\n
64 \u2013 8 = 56 (m)<\/p>\n
Chi\u1ec1u r\u1ed9ng mi\u1ebfng \u0111\u1ea5t \u0111\u01b0\u1ee3c t\u0103ng th\u00eam s\u1ed1 m\u00e9t l\u00e0:<\/p>\n
56 \u2013 34 = 22 (m)<\/p>\n
Di\u1ec7n t\u00edch ph\u1ea7n t\u0103ng theo chi\u1ec1u r\u1ed9ng mi\u1ebfng \u0111\u1ea5t l\u00e0:<\/p>\n
56 x 22 = 1232 (m2<\/sup>)<\/p>\n
\u0110\u00e1p s\u1ed1: St\u0103ng theo<\/sub> chi\u1ec1u r\u1ed9ng<\/sub> = 1232 (m2<\/sup>)<\/p>\n
Tr\u00ean \u0111\u00e2y l\u00e0 c\u00e1c c\u00f4ng th\u1ee9c\u00a0t\u00ednh chu vi h\u00ecnh ch\u1eef nh\u1eadt, di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt, c\u00e1c b\u00e0i t\u1eadp v\u1eadn d\u1ee5ng li\u00ean quan \u0111\u1ebfn h\u00ecnh ch\u1eef nh\u1eadt. Hi v\u1ecdng r\u1eb1ng s\u1ebd gi\u00fap c\u00e1c b\u1ea1n v\u1eadn d\u1ee5ng v\u00e0 h\u1ecdc th\u1eadt t\u1ed1t.<\/p>\n
- C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt:<\/li>\n<\/ol>\n
- C\u00f4ng th\u1ee9c t\u00ednh chu vi h\u00ecnh ch\u1eef nh\u1eadt:<\/li>\n<\/ol>\n