We start with the more complicated side which is the left side, and show that, on using some trigonometric identities, we will get the term on the right side .

Using Quotient identity for tangent function, we will get


Taking out sine function from the numerator

Cancelling the common term of numerator and denominator

Answer:
0
Step-by-step explanation:
First, you plug -9 into g(x) and you get g(-9) = - 1. After that, you solve f(-1), which you then reach the solution of 0 by solving.