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{"id":22419,"date":"2018-03-19T17:44:25","date_gmt":"2018-03-19T10:44:25","guid":{"rendered":"https:\/\/lop12.edu.vn\/?p=22419"},"modified":"2018-03-19T17:44:53","modified_gmt":"2018-03-19T10:44:53","slug":"hinh-hoc-chuong-1-bai-4-the-tich-cua-khoi-da-dien","status":"publish","type":"post","link":"https:\/\/lop12.edu.vn\/hinh-hoc-chuong-1-bai-4-the-tich-cua-khoi-da-dien\/","title":{"rendered":"H\u00ecnh h\u1ecdc – Ch\u01b0\u01a1ng 1 – B\u00e0i 4 – Th\u1ec3 t\u00edch c\u1ee7a kh\u1ed1i \u0111a dien"},"content":{"rendered":"

B\u00e0i 15 (trang 28 sgk H\u00ecnh H\u1ecdc 12 n\u00e2ng cao):<\/b><\/p>\n

Cho tam gi\u00e1c ABC c\u1ed1 \u0111\u1ecbnh v\u00e0 m\u1ed9t \u0111i\u1ec3m S thay \u0111\u1ed5i. Th\u1ec3 t\u00edch c\u1ee7a kh\u1ed1i ch\u00f3p S.ABC c\u00f3 thay \u0111\u1ed5i hay kh\u00f4ng n\u1ebfu:<\/p>\n

a) \u0110\u1ec9nh S di chuy\u1ec3n tr\u00ean m\u1ed9t m\u1eb7t ph\u1eb3ng song song v\u1edbi m\u1eb7t ph\u1eb3ng (ABC)?<\/p>\n

b) \u0110\u1ec9nh S di chuy\u1ec3n tr\u00ean m\u1ed9t m\u1eb7t ph\u1eb3ng song song v\u1edbi ch\u1ec9 m\u1ed9t c\u1ea1nh \u0111\u00e1y?<\/p>\n

c) \u0110\u1ec9nh S di chuy\u1ec3n tr\u00ean m\u1ed9t \u0111\u01b0\u1eddng th\u1eb3ng song song v\u1edbi m\u1ed9t c\u1ea1nh \u0111\u00e1p?<\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Trong \u0111\u00f3 S\u0394ABC<\/sub>\u00a0kh\u00f4ng \u0111\u1ed5i, h = d(S; (ABC))<\/p>\n

 <\/p>\n

a) Khi S di chuy\u1ec3n tr\u00ean (\u03b1)\/\/ (ABC)) th\u00ec d(S, (ABC)) = (d(\u03b1);(ABC))kh\u00f4ng \u0111\u1ed5i n\u00ean VVS.ABC<\/sub>\u00a0kh\u00f4ng \u0111\u1ed5i.<\/p>\n

b) Khi S di chuy\u1ec3n tr\u00ean m\u1ed9t m\u1eb7t ph\u1eb3ng song song v\u1edbi m\u1ed9t c\u1ea1nh \u0111\u00e1y. M\u1eb7t ph\u1eb3ng n\u00e0y c\u00f3 th\u1ec3 kh\u00f4ng song song v\u1edbi mp (ABC).<\/p>\n

Khi \u0111\u00f3 h = d(S: (ABC)) c\u00f3 th\u1ec3 thay \u0111\u1ed5i n\u00ean VS.ABC<\/sub>\u00a0c\u00f3 th\u1ec3 thay \u0111\u1ed5i.<\/p>\n

c) Gi\u1ea3 s\u1eed S di chuy\u1ec3n tr\u00ean d v\u00e0 d\/\/ AC (d \/\/ AC => d \/\/(ABC)) d(S, (ABC)) , (ABC)=d(d; (ABC)) kh\u00f4ng \u0111\u1ed5i n\u00ean VVS.ABC<\/sub>\u00a0kh\u00f4ng \u0111\u1ed5i.<\/p>\n

B\u00e0i 16 (trang 28 sgk H\u00ecnh H\u1ecdc 12 n\u00e2ng cao):<\/b>\u00a0H\u00e3y chia m\u1ed9t kh\u1ed1i t\u1ee9 di\u1ec7n th\u00e0nh hai kh\u1ed1i t\u1ee9 di\u1ec7n sao cho t\u1ec9 s\u1ed1 th\u1ec3 t\u00edch c\u1ee7a hai kh\u1ed1i n\u00e0y b\u1eb1ng s\u1ed1 k > 0 cho tr\u01b0\u1edbc.<\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

<\/div>\n

\"\"<\/p>\n

G\u1ecdi M l\u00e0 m\u1ed9t \u0111i\u1ec3m tr\u00ean c\u1ea1nh AB kh\u00e1c hai \u0111\u1ea7u n\u00fat). Khi \u0111\u00f3 (SMC) chia t\u1ee9 di\u1ec7n S.ABC th\u00e0nh hai t\u1ee9 di\u1ec7n S.AMC v\u00e0 S. BMC l\u1ea7n l\u01b0\u1ee3t v\u1edbi th\u1ec3 t\u00edch V1<\/sub>,2<\/sub><\/p>\n

V\u00ec d(S, (AMC) = d(S,(BMC)) n\u00ean<\/p>\n

\"\"<\/p>\n

K\u1ebft lu\u1eadn: L\u1ea5y \u0111i\u1ec3m M tr\u00ean AB sao cho AM = k MB. Khi \u0111\u00f3, kh\u1ed1i t\u1ee9 di\u1ec7n SABC \u0111\u01b0\u1ee3c chia th\u00e0nh hai kh\u1ed1i t\u1ee9 di\u1ec7n SAMC v\u00e0 SBMC th\u1ecfa y\u00eau c\u1ea7u b\u00e0i to\u00e1n.<\/p>\n

B\u00e0i 17 (trang 28 sgk H\u00ecnh H\u1ecdc 12 n\u00e2ng cao):<\/b><\/p>\n

T\u00ednh th\u1ec3 t\u00edch c\u1ee7a kh\u1ed1i h\u1ed9p ABCD.A\u2019B\u2019C\u2019D\u2019 bi\u1ebft r\u1eb1ng AA\u2019B\u2019D\u2019 l\u00e0 kh\u1ed1i t\u1ee9 di\u1ec7n \u0111\u1ec1u c\u1ea1nh a.<\/p>\n

\"\"<\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n

V\u00ec h = d (ABCD); (A\u2019B\u2019C\u2019D\u2019) = d(A, (A\u2019B\u2019D\u2019) v\u00e0 S\u0394A’ B’ C’ D’<\/sub>=2.S\u0394A’ B’ D’<\/sub><\/p>\n

\"\"<\/p>\n

B\u00e0i 18 (trang 28 sgk H\u00ecnh H\u1ecdc 12 n\u00e2ng cao):<\/b>\u00a0T\u00ednh th\u1ec3 t\u00edch c\u1ee7a m\u1ed9t kh\u1ed1i n \u2013 c\u00f3 t\u1ea5t c\u1ea3 c\u00e1c c\u1ea1nh \u0111\u1ec1u b\u1eb1ng a.<\/p>\n

\"Gi\u1ea3i<\/p>\n

L\u1eddi gi\u1ea3i:<\/b><\/p>\n