1/4sin^2a+2/5cos^2a 求值
已知cos(a/2)-sin(a/2)=1/5,求值tan a
sin^a+cos^(π/6+a)+1/2sin(2a+π/6)求值
求值4sin^2a-3sinacosa-5cos^2a
已知(tan a-3)(sin a+cos a+3)=0,求值:2/3sin²a+1/4cos²a
求值sin^2a+cos^2a(π/6+a)+1/2sin(2a+6/π)
先化简,再求值:(sin a-cos a)÷(sin a+cos a),其中tan a=2
求值:1-sin^6a-cos^6a/1-sin^4a-cos^4a
已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=
求值sin^2A+cos^2(A+30°)+sinAcos(A+30°)
化简 1-sin^4a-cos^4a/cos^2a-cos^4a
证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A
化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)==