化简sin^2a+sin^2b-sin^2a*sin^2b+cos^2a*cos^2b

sin^2 (A)+sin^2(B)-sin^2(A)sin^2(B)+cos^2(A)cos^2(B) 证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2 若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a 化简[sin(2A+B)]/sinA-2cos(A+B) 为什么sin(a+b)-sina=2sin（b/2）cos（a+b/2） 证明三角函数等式sin(A+B)-sinA=2cos(A+B/2)sin(B/2) 求证.(2),sin平方a+sin平方b-sin平方a*sin平方b+cos平方a*cos平方b=1 sin^2A-cos^2B=0化简 化简sin^2(a)*sin^2(b)+cos^2(a)*cos^2(b)-1/2cos2a*cos2b 已知向量a=(cosα,sinα) b=(cosβ,sinβ) |a+b|=2|a-b| Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2 a*sin(x)+b*cos(x)化简 其结果是 sqrt(a^2+b^2)*sin(x+arctan(a/b))吗