[急] -sinθ/cosθ + cosθ/sinθ點計

正確做法是

tan(270°+θ) - cos(-θ)/sin(θ+180°)
= - cotθ - cosθ/(-sinθ)
= - cotθ + cosθ/sinθ
= - cotθ + cotθ
= 0

注意tan(270+θ)不等於-tanθ啊
tan(270°+θ)= - cotθ (90°或270°函數要改變)

The answer is 0.

tan(270°+θ) ≠ - tan θ