C. I don't know how to tell you to do it. But hopefully your teacher will allow you to use a calculator. If so you know that sin 36 can not = the same as sin 54 or sin 64 so you can rule those out automatically. That will leave you with cos so try in your calculator cos 54 and cos 64 usually which ever is the closest number to the number you start out with will be your answer. Hope this helped some.
