Consider LHS

Thus we have

Questions like these are not as hard as you may think. here are some tips:

- Start on the most complicated side, it gives you more options to change stuff

- It is usually a good idea to change everything to sines and cosines. these are the functions students are most familiar with and so it is easy to see connections

- Always work one side to get the other, if you can't, make one side as simple as possible, stop, and then try to work the other side to get the simplified expression.

Now, try the other proving questions