trigonometric function (M2)

1)
圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701102260083713873384530.jpg

Find x for
圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701102260083713873384541.jpg



2) i) Express
圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701102260083713873384542.jpg
in term of difference of sine functions.
ii) By mathematical induction, prove the following equation for all positive integer n.

圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701102260083713873384553.jpg


iii) Find the value of

圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701102260083713873384554.jpg


iv) Show that

圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701102260083713873384566.jpg


v) Find cos(72) in surd form.