Marty is proving that the following trigonometric identity is true: tan2θ⋅cos2θ=1−cos2θ which step would be the first line of his proof?

Step-by-step explanation:

We have been given a trigonometric identity . We are asked to determine the first step of the proof.

We will use identity to prove our given identity.

From above identity, we will get:

So, we will substitute is our given identity as:

Therefore, the first line of the proof would be .

Upon dividing both sides of equation by , we will get:

Hence proved.