Sin(π+2a)/(1+cos2a) 化简.
化简[cos(4a-π/2)*sin(π/2-a)*cos2a]/[(1+cos2a)(1+cos4a)*cosa
化简:sin2a/sin(π+a)+cos2a+1/cosa
cos2a-1+2sin^2a
已知sin a+cos a=1/3,a属于(π/2,π),求cos2a
化简[2sin2a/(1+cos2a)]*(cos^2a/cos2a)
化简sin^2(a)*sin^2(b)+cos^2(a)*cos^2(b)-1/2cos2a*cos2b
求证:sin a (1+cos2a)=sin a cos a
求证:2sin(π/4+a)sin(π/4-a)=cos2a
证明:2sin(π/4+a)sin(π/4-a)=cos2a
已知tan(π+a)=-1/3求[sin(π-2a)+cos^2a]/[2cos2a+sin2a+2]
若a∈(0,π/2)且sin^2 a+cos2a=1/4,求tan a的值
已知sin²2a+sin2acosa-cos2a=1,a属于(0,π/2),求sina,tana