Tr\u1ea3 l\u1eddi c\u00e2u h\u1ecfi To\u00e1n 10 \u0110\u1ea1i s\u1ed1 B\u00e0i 3 trang 149<\/strong>: H\u00e3y ch\u1ee9ng minh c\u00f4ng th\u1ee9c sin(a + b) = sina cosb + cosa sinb.<\/ins><\/p>\n\n\n\nL\u1eddi gi\u1ea3i<\/strong><\/p>\n
L\u1eddi gi\u1ea3i<\/strong><\/p>\n