Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2
Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2
cos(a+B)×cos(a-B)=1/3,求cos^2(a)-sin^2(B)的值
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
已知tan(a+b)=2/5,tan(b-pai/4)=1/4,求(cos a+sin a)/(cos a-sin a)
cos(a-b)=12/13,sin(a+b)=-3/5,求cos(pai/2-2a)
已知向量a=(sinθ,cosθ-2sinθ),向量b=(1,2) 求tanθ 求sinθ*cosθ-3cos^2θ
已知cos(a+b)=-1/3,cos 2a=-5/13,a,b均为钝角,求sin(a-b)
已知0<A<π/2<B<π,cos(B-π/4)=1/3,sin(A+B)=4/5求cos(a+
由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a
cos(a+b)=cos(a)*cos(b)-sin(a)*sin(b) 用三角形证明
a,b为锐角,cos(a-b/2)=根号3/2,sin(a/2-b)=-1/2,求cos(a+b)
求证sin平方a * sin平方b+cos平方a * cos平方b-1/2cos2a *cos2B=1/2