求证sin^2a+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)
求证:tan a/2=(1-cos)/sin a=sin a/(cos a+1)
求证sin^4a+cos^4a=1-2sin²acos²a
求证 cos(A)+ 根号3sin(A)=2sin(π/6+A)
求证:cos²x+cos²(x+a)-2cosxcosacos(x+a)=sin³a
求证sin(90+a)=cos a
求证 2(1-sin a)(1+cos a)=(1-sin a + cos a)^2
求证:2[1+sin(派+a)][1+cos(-a)]=[1-sin(派-a)-cos(派-a)]
求证:sin a (1+cos2a)=sin a cos a