若sin^2a+2cos^2b=2cosa,求sin^2a+cos^2b最大最小值
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
若cos(a+B)*cosa+sin(a+B)*sina=-4/5,则sin(π/2-B)
Cos(a+b)*cos(a-b)=1/5 求cos ^2-sin^2
cos^2A - cos^2B + sin^2C=2cosA *sinB *sinC证明
cos^2A - cos^2B + sin^2C=2cosA *sinB *sinC
求证: sina+sinb=2sin[(a+b)/2]cos[(a-b)/2] cosa+cosb=2cos[(a+b)
三角形ABC中,cosA=3/5,求cos^(A/2)-sin(B+C)的值
已知3cos^2a+2sin^2B=2cosa,求cos^2a+sin^2B的取值范围
已知cosa-cosb=1/3,sin-sinb=1/2.求cos(a-b)的值 化简:cos^2(a+45度)-sin
已知cosa-cosb=1/2,sina-sinb=-1/3,求cos(a-b),sin(a+b)
已知sina+sinB=-2/3,cosa-cosB=1/3.求cos(a+B),sin(a+B)
cos(a+B)×cos(a-B)=1/3,求cos^2(a)-sin^2(B)的值