tanα= sinα/cosα= 3 sinα= 3 cosαsin 2α+cos 2α= 1。

So sin α = 3 √10/10cosα = √10/0.

1 original formula = (12cosα-2cosα)/(5cosα+9cosα) = 5/7.

2 The original formula = 3 √10/10 * √10 = 3/10.

3 Original formula = (3 √10//kloc-0+√10/10) 2 = 8/5.

3 1 Not true-1≤ cos α≤1(cos α) 2≤1.

2 keep -π/4 >- 1