This proof shows the first five steps for verifying cot^2 (x/2)= cos x+1/cos c-1 use the drop down boxes to complete the steps of the proof

1. Tangent Half-angle identity

2. 1 + cos x

3. 1 - cos x

Step-by-step explanation:

Just answered the question on edge

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.