>>943
ん?
(tanθ)^2 - (tanθ)^2 (sinθ)^2 - (sinθ)^2
=(tanθ)^2 - (sinθ)^2 ((tanθ)^2+1)
=(tanθ)^2 - (sinθ)^2/(cosθ)^2
=0
だが。