若cos(a+b)cos(a-b)=1/3,则cos²a-sin²b的值
cos(a+B)×cos(a-B)=1/3,求cos^2(a)-sin^2(B)的值
若cos(A+B)cos(A-B)=1/3 则cos平方A-sin平方B 等于
若cos(a+b)·cos(a-b)=1/3,则cos^2 a-sin^2 b的值是?
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a
1.若sin a+sin b=ㄏ2/2,则cos a+cos b的取值范围是多少?
sin²(a+b)+cos²(a+b)=
cos(a+b)=cos(a)*cos(b)-sin(a)*sin(b) 用三角形证明
cos^B-cos^C=sin^A,三角形的形状
sin(a-b)=1,sin a=1/3,求cos b的值
Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2
已知4sin asin b=根号2,4cos a cos b=根号6,则cos 2a+cos 2b的值是?