Chứng minh sin^2x-cos^2x + cos^4x /cos^2x-sin^2x + sin^4x = tan ^ 4 x
Giải thích
sin2x−cos2x+cos4xcos2x−sin2x+sin4x=cos4x+1−2cos2xsin4x+2cos2x−1=cos4x−cos2xsin4x+cos2x=cos2x2−cos2xsin2x2+cos2x=cos2x+124−cos2x1−cos2x24+cos2x=cos22x−2cos2x+11+2cos2x+cos22x=cos2x−121+cos2x2=−2sin2x22cos2x−1+12=sin4xcos4x=tan4x