I am doing a non-credit assignment and would like to check my answers to see if I have done them correctly, If you can provide help, show steps and/or show me final answer to the following questions it would greatly assist me to see if I am doing these correctly, Thank you!

Question 1:

The exact value of cos(105) can be determined using the sum and difference identities. Determine the exact value of cos(105) and express the answer in the form

Question 2:

Prove the Following algebraically;

Question 3:

Solve the following equation for x, where