若sin^2a+2cos^2b=2cosa,求sin^2a+cos^2b最大最小值sin^2α+2sin^2β=2cosα,求sin^2α+sin^2β的最大值和最小值!

求证cos(a+b)cos(a－b)=cos^2b－sin^2a 求证cos(a+b)cos(a-b)=cos^2a-sin^2b 化简cos(a+b)cos(a-b)+sin^2b Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2 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) cos^2a-cos^2b=m,那么sin(a+b)sin(a-b)=? 证明sin(A+B)sin(A-B)=cos^2B-cos^2A sin(a-b)*cos a-cos(a-b)*sin a=1/5,则cos 2b的值是 证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2B=1 sin^4+sin^2cos^2+cos^2a= 若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a=1.(不用向量怎么证?) 若log2/1(sin a)+log2/1(sin b)=2,(27^cos a)^cos b=1/9,cos(2a+2b)=? 求证1+sin a+cos a+2sin acos a/1+sin a+cos a=sin a+cos a 求证sin^2(a-b)+2cos(a-b)cosacosb= cos^2a+cos^2b如题 已知cos(a+b)cos(a-b)=1/3,则cos^2a-sin^2b的值是? cos(a+B)×cos(a-B)=1/3,求cos^2(a)-sin^2(B)的值 化简sin^2acos^b-cos^2asin^2b+cos^a-cos^2b 已知a=(2cosα,2sinα),b=(5cosβ,5sinβ),若a·b=-5,则cos=