Giai cac pt sau:
a) cos ^3(x)*cos(3x) + sin^3(x)*sin(3x) = (can 2)/4
b) cau b nay em go hoi phuc tap, moi ng doc ki nhe:
(sin^6(x) + cos^6(x))/(tan(x-pi/4)*tan(x+pi/4)) = -1/4
c) 2cos(13x) + 3(cos(5x) + cos(3x)) = 8cos(x)*cos^3(4x)
d) 2cos^2(x) + 2cos^2(2x) + 2cos^2(3x) - 3 = cos(4x)(2sin(2x) + 1)
e) 4*(can 3)*sin(x)cos(x)sin(2x) = sin(8x)
f) sin^8(x) + cos^8(x) = 2(sin^10(x) + cos^10(x)) + 5/4*cos(2x)
- thang1308 yêu thích