[急] F.4數學, 有20點

寫個計算步驟出來. 要準確&詳細!!

13.
sin(30-x) cos(30-x) = (root3) /2
The ans. is 120', 150', 300', 330'

6.
tan^2 x + cot^2 x = 2
ans. 180'n +- 45'

8.
sin 4x + sin x = 0
ans. 72'n or 240'n +- 60'

10.
sin x = cot 2x
ans. 120'n + 30' or 360'n - 90'

14.
cos x + cos 7x = cos 4x
ans. 90'n +- 22.5' or 120'n +- 20'