怎么证明sin^2(a)+cos^2(a+30)+sinacos(a+30)=3/4
求值sin^2A+cos^2(A+30°)+sinAcos(A+30°)
1已知sina+cosa=-7/5 求tana-cota2已知sin(a-3π)=2cos(a-4π) 求sinacos
高一数学已知sinacos(a-b)+sin(b-a)sin(π/2-a)=-4/5,求cos(π/2+b)的值
已知tana=3 求根号下(sin^4a-3sinacos^3a+cos^4a)
证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A
证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a
若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a
证明tan a/2=sin a/(1+cos a)
证明: sin^2a+cos^2a=1
证明:cos^4 a-sin^4 a=cos^2 a(1-tan a)(1+ tan a)
tan a/2=(1-cos a)/sin a=sin a/(1+cos a)如何证明?
怎么证明:sin平方A+cos平方A=1