求函数y=tan(2x/3)的周期.
已知sinA=4/5,求sin(A/2),cos(A/2),tan(A/2),sin2A,cos2A,tan2A.
设3tan-1=tan-1(1/x)+tan-1(1/3),试求x之值.
试证下列恒等式cosA+cosB+cosC+cos(A+B+C)=4 cos(B+C)/2cos(C+A)/2cos(A+B)/2
试解方程式 csc3θ + sec²θ = sinθcsc2θsec3θ.
设x,y,z为任意三个角,求证:sinx+siny+sinz-sin(x+y+z)=4 sin(x+y)/2 sin(y+z)/2 sin(z+x)/2
设x,y,z为任意三个角,求证:sinxsin(y-z)cos(y+z-x)+sinysin(z-x)cos(z+x-y)+sinzsin(x-y)cos(x+y-z)=0