step 1:

9)

Reciprocal trigonometric identity

Double angle formula for tangent function is

Since

.

Step 2:

10)

Reciprocal trigonometric identity

Double angle formula for tangent function is

Since

Step 3:

11)

Reciprocal trigonometric identity .

Half angle formula for cosine function:

step 4:

12)

Reciprocal trigonometric identity

Double angle formula for tangent function is

Since 

step 5:

13)

Reciprocal trigonometric identity

Double angle formula for tangent function is

Substitute in

Step 6:

14)

Reciprocal trigonometric identity

Double angle formula for tangent function is

Substitute value in double angle expression.