>>602
>3cos3θcos(π/3-θ)=sin3θsin(π/3-θ)
t=π/3-θ
3θ=π-3t
3cos(π-3t)cost=sin(π-3t)sint
-3cos3tcost=sin3tsint
3cos3tcost+sin3tsint=0
2cos4t+4cos2t=0
s=2t
cos2s+2coss=0
2cos^2s+2coss-1=0
coss=cos2t=(-2+√3)/2
2cos^2t=1+(-2+√3)/2=√3/2
0＜t＜π/3
cost=cos(π/3-θ)=√(√3/2)>√3/2
0<t<π/6
π/6<θ<π/3
(1/2)cosθ+(√3/2)sinθ=√(√3/2)
cos^2θ+sin^2θ=1
cosθ=(√(2√3)+√(12-6√3))/4
sinθ=(√(6√3)-√(4-2√3))/4
y=(1/2)sin3θ/cos(π/3-θ)=(1/2)(3sinθ-4sin^3θ)/cost
=(1/2)-√3+√(45+42√3)/6