In terms of pi means to include pi in your answer. In other words, don't use 3.14 or 22/7 for pi.
Answer:
The Pythagorean identity states that
Using that we can rewrite the left denominator as:
Which can be factored as
The numerator we can expand as:
On the right hand side, let's multply numerator and denominator with (1 - sin t):
The total formula then becomes:
There you go... left and right are equal.
"color the piece according to your color chart." Do you have that? If you don't, I wouldn't worry, you still did all the work and got all the answers, so your teacher should be fine with it.