sin cos tan

1)
tanθ/sinθcosθ
=(sinθ/cosθ)/sinθcosθ
=sinθ/cosθ * 1/sinθcosθ
=1/cos²θ

2)
- 5sin²θ - 5cos²θ
= - 5(1 - cos²θ) - 5cos²θ
= - 5 + 5cos²θ - 5cos²θ
= -5

3)
sinθ=cos 35°
θ=55° or θ=125°

2015-01-01 21:11:34 補充：
Or you can answer question 3 like this,
sinθ=cos 35°
sinθ=sin(90° - 35°)
sinθ=sin 55°
θ=55° or θ=180° - 55° = 125° (∵sin 55° = sin 125°)