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{"id":9743,"date":"2018-07-17T21:45:14","date_gmt":"2018-07-17T14:45:14","guid":{"rendered":"https:\/\/onthitot.com\/?p=9743"},"modified":"2018-07-17T21:45:14","modified_gmt":"2018-07-17T14:45:14","slug":"cong-thuc-tinh-dien-tich-cua-mot-so-hinh-co-ban-va-bai-tap-lop-4","status":"publish","type":"post","link":"https:\/\/onthitot.com\/cong-thuc-tinh-dien-tich-cua-mot-so-hinh-co-ban-va-bai-tap-lop-4\/","title":{"rendered":"C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch c\u1ee7a m\u1ed9t s\u1ed1 h\u00ecnh c\u01a1 b\u1ea3n v\u00e0 b\u00e0i t\u1eadp l\u1edbp 4"},"content":{"rendered":"

D\u01b0\u1edbi \u0111\u00e2y onthitot.com t\u1ed5ng h\u1ee3p m\u1ed9t s\u1ed1 c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch c\u1ee7a c\u00e1c h\u00ecnh c\u01a1 b\u1ea3n. B\u00e0i vi\u1ebft n\u00e0y gi\u00fap c\u00e1c b\u1ea1n h\u1ecdc sinh \u00f4n luy\u1ec7n t\u1ed5ng h\u1ee3p l\u1ea1i c\u00e1c ki\u1ebfn th\u1ee9c t\u00ednh to\u00e1n di\u1ec7n t\u00edch c\u1ee7a c\u00e1c h\u00ecnh.<\/p>\n

I\/ C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch c\u1ee7a m\u1ed9t s\u1ed1 h\u00ecnh c\u01a1 b\u1ea3n<\/h2>\n

1\/ C\u00f4ng th\u1ee9c di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt<\/h3>\n

S = a. b<\/p>\n

trong \u0111\u00f3 ta c\u00f3:<\/p>\n

a: l\u00e0 \u0111\u1ed9 d\u00e0i chi\u1ec1u r\u1ed9ng c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt<\/p>\n

b l\u00e0 \u0111\u1ed9 d\u00e0i chi\u1ec1u d\u00e0i c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt<\/p>\n

2\/ C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch h\u00ecnh vu\u00f4ng<\/h3>\n

S = a2<\/sup> (a l\u00e0 chi\u1ec1u d\u00e0i c\u1ee7a 1 c\u1ea1nh)<\/p>\n

3\/ Di\u1ec7n t\u00edch h\u00ecnh b\u00ecnh h\u00e0nh<\/h3>\n

S = a.h<\/p>\n

Trong \u0111\u00f3:<\/p>\n

a: Chi\u1ec1u d\u00e0i c\u1ee7a 1 c\u1ea1nh<\/p>\n

h: chi\u1ec1u cao c\u1ee7a h\u00ecnh b\u00ecnh h\u00e0ng t\u01b0\u01a1ng \u1ee9ng v\u1edbi a.<\/p>\n

4\/ Di\u1ec7n t\u00edch h\u00ecnh thoi<\/h3>\n

S = \u00bd a.b (a, b l\u00e0 \u0111\u1ed9 d\u00e0i hai \u0111\u01b0\u1eddng ch\u00e9o)<\/p>\n

5\/ C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch tam gi\u00e1c<\/h3>\n

S = \u00bd b.h<\/p>\n

Trong \u0111\u00f3:<\/p>\n

b: \u0111\u1ed9 d\u00e0i c\u1ea1nh \u0111\u00e1y<\/p>\n

h: chi\u1ec1u cao c\u1ee7a t\u00ecnh tam gi\u00e1c<\/p>\n

6\/ Di\u1ec7n t\u00edch h\u00ecnh tr\u00f2n<\/h3>\n

S = \u03c0 . R2<\/sup> (R : b\u00e1n k\u00ednh c\u1ee7a h\u00ecnh tr\u00f2n)<\/p>\n

7\/ Di\u1ec7n t\u00edch h\u00ecnh Thang<\/h3>\n

S = \u00bd (a + b).h<\/p>\n

Trong \u0111\u00f3:<\/p>\n

a, b: chi\u1ec1u d\u00e0i hai c\u1ea1nh \u0111\u00e1y<\/p>\n

h: chi\u1ec1u cao c\u1ee7a h\u00ecnh thang<\/p>\n

II\/ B\u00e0i t\u1eadp<\/h2>\n

B\u00e0i 1: Cho tam gi\u00e1c vu\u00f4ng ABC vu\u00f4ng g\u00f3c t\u1ea1i \u0111i\u1ec3m B, c\u1ea1nh \u0111\u00e1y BC c\u00f3 chi\u1ec1u d\u00e0i l\u00e0 5cm, chi\u1ec1u cao c\u1ee7a tam gi\u00e1c ABC l\u00e0 2 cm. T\u00ednh di\u1ec7n t\u00edch c\u1ee7a tam gi\u00e1c vu\u00f4ng ABC?<\/p>\n

\"\"<\/p>\n

Gi\u1ea3i:<\/p>\n

Ta c\u00f3 c\u1ea1nh \u0111\u00e0y BC = 5cm v\u00e0 chi\u1ec1u cao h = 2cm.<\/p>\n

T\u1eeb \u0111\u00f3 suy ra S = \u00bd BC.h = \u00bd .5.2 = 5 cm<\/p>\n

B\u00e0i 2: Cho h\u00ecnh ch\u1eef nh\u1eadt ABCD c\u00f3 \u0111\u1ed9 d\u00e0i c\u1ea1nh AB = 6cm v\u00e0 \u0111\u1ed9 d\u00e0i c\u1ea1nh BD = 3cm. T\u00ednh di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt ABCD<\/p>\n

Gi\u1ea3i:<\/p>\n

Theo c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n tich h\u00ecnh ch\u1eef nh\u1eadt ta c\u00f3<\/p>\n

S = AB.BD = 6.3 = 18cm<\/p>\n

B\u00e0i 3: Cho h\u00ecnh thang ABCD c\u00f3 \u0111\u1ed9 d\u00e0i c\u00e1c c\u1ea1nh l\u00e0 AB = 8cm, c\u1ea1nh \u0111\u00e1y CD = 13cm, chi\u1ec1u cao gi\u1eefa 2 c\u1ea1nh \u0111\u00e1y c\u1ee7a h\u00ecnh thang l\u00e0 7cm. T\u00ednh di\u1ec7n t\u00edch h\u00ecnh thang ABCD<\/p>\n

Gi\u1ea3i:<\/p>\n

Theo b\u00e0i ta c\u00f3 chi\u1ec1u cao c\u1ee7a h\u00ecnh thang l\u00e0 h = 7 cm<\/p>\n

Theo c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch h\u00ecnh thang ta c\u00f3<\/p>\n

S = \u00bd (AB + CD).h = \u00bd (8 + 13).7 = 73,5 cm<\/p>\n

B\u00e0i 4: Cho m\u1ed9t h\u00ecnh tr\u00f2n C c\u00f3 \u0111\u01b0\u1eddng k\u00ednh AB = 10 cm. T\u00ednh di\u1ec7n t\u00edch h\u00ecnh tr\u00f2n?<\/p>\n

\"\"<\/p>\n

Gi\u1ea3i:<\/p>\n

Ta c\u00f3 \u0111\u01b0\u1eddng k\u00ednh c\u1ee7a h\u00ecnh tr\u00f2n l\u00e0 d=10cm. => R = \u00bd d = \u00bd .10 = 5 cm<\/p>\n

Di\u1ec7n t\u00edch h\u00ecnh tr\u00f2n:<\/p>\n

S = \u03c0. R2<\/sup> = 3,14. 52<\/sup> = 15,7 cm<\/p>\n

B\u00e0i 5: Cho h\u00ecnh thoi ABCD c\u00f3 \u0111\u1ed9 d\u00e0i c\u00e1c \u0111\u01b0\u1eddng ch\u00e9o c\u1eaft nhau l\u00e0 b\u1eb1ng 6 cm v\u00e0 8 cm. T\u00ednh di\u1ec7n t\u00edch h\u00ecnh thoi n\u00e0y?<\/p>\n

Gi\u1ea3i:<\/p>\n

Theo c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch h\u00ecnh thoi th\u00ec ta c\u00f3 a = 6 cm v\u00e0 b = 8cm. => S = \u00bd (a .b) = \u00bd (6 x 8) = 21cm<\/p>\n

Tr\u00ean \u0111\u00e2y l\u00e0 m\u1ed9t s\u1ed1 b\u00e0i t\u1eadp \u00e1p d\u1ee5ng c\u00e1c c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch. M\u1ed9t s\u1ed1 h\u00ecnh c\u00f2n l\u1ea1i c\u00e1c b\u1ea1n c\u00f3 th\u1ec3 d\u1ef1a v\u00e0 c\u00e1c c\u00f4ng th\u1ee9c \u0111\u1ec3 c\u00f3 th\u1ec3 t\u00ednh \u0111\u01b0\u1ee3c di\u1ec7n t\u00edch c\u00e1c h\u00ecnh<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

D\u01b0\u1edbi \u0111\u00e2y onthitot.com t\u1ed5ng h\u1ee3p m\u1ed9t s\u1ed1 c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch c\u1ee7a c\u00e1c h\u00ecnh c\u01a1 b\u1ea3n. B\u00e0i vi\u1ebft n\u00e0y gi\u00fap c\u00e1c b\u1ea1n h\u1ecdc sinh \u00f4n luy\u1ec7n t\u1ed5ng h\u1ee3p l\u1ea1i… <\/p>\n","protected":false},"author":9,"featured_media":9746,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[412,406],"tags":[],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/posts\/9743"}],"collection":[{"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/comments?post=9743"}],"version-history":[{"count":0,"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/posts\/9743\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/media\/9746"}],"wp:attachment":[{"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/media?parent=9743"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/categories?post=9743"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/onthitot.com\/wp-json\/wp\/v2\/tags?post=9743"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}