Verify the identity. justify each step

Remember: We have to work from either the LHS or the RHS.
(Left hand side or the Right hand side)

You should already know this:

1.


2.


3.


So, our question is:



Plug in the first two identities I gave you.



Apply the first identity I said you needed to know on 1/(tan θ). We should get:



Multiply the first fraction by sinθ, on both the numerator and denominator.
Multiply the second fraction by cosθ, on both the numerator and denominator.


Now, use the third identity I said that you needed to know to simplify the numerator.



LHS = RHS

Therefore, identity is verified.

I'm a bit puzzled here because they did not provide you with any measures of the other angles, so i am unable to provide a theorem or postulate to support my answer, but i'd say 90 degrees because it looks closer to a right angle than anything.