化简 sin^4a-cos^4b

化简 sin^4a-cos^4b 化简cos^4b-sin^4b 由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a sin b解题设a为锐角,证：1、2分之根3乘cos a + 2分之1乘sin a=cos(6分之π-a)2、cos a-sin a=根号2cos(4分之π+a) sin(a)*cos(a)=4,那么sin(a) cos(b)=? cos^4A-sin^4a 化简 当a=3π/4时,sin(a+b)+cos(a+b)+sin(a-b)+cos(a-b) 化简COS(a+B)COS(a-B)+sin平方B 化简cos(a+b)cos(a-b)+sin^2b 化简1-sin^4a-cos^4a/1-sin^6a-cos^6a 1-sin^6a-cos^6a分之1-sin^4a-cos^4a 化简 化简：sin^4a+cos^2a-sin^2a-cos^4a 已知 sin a +sin b =1/4cos a +cos b =1/3求 tan (a+b) cos(a+b)+cos(a-b)/sin(a+b)+sin(a-b)化简 化简 cos(a-b)cos(a+b)+sin(a-b)sin(a+b). cos(a-b)cos(a+b)+sin(a-b)sin(a+b)化简, 化简：(sin^6a+cos^6a-1) / (sin^4ª+cos^4a-1) 化简 1-sin^4a-cos^4a/cos^2a-cos^4a 化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)==