Biểu thức C = 2(sin^4 x + cos^4 x + sin^2 x cos^2 x)^2 - (sin^8 x + cos^8 x
Giải thích
Đáp án C
Ta có:
C=2sin4x+cos4x+sin2xcos2x−2sin8x+cos8x=2sin2x+cos2x2−sin2xcos2x2−sin4x+cos4x2−2sin4xcos4x=21−sin2xcos2x2−sin2x+cos2x2−2sin2xcos2x+22sin4xcos4x=21−sin2xcos2x2−1−2sin2x.cos2x+22sin4xcos4x=21−2sin2xcos2x+sin4xcos4x−1−4sin2xcos2x+4sin4xcos4x+2sin4xcos4x=1