#4: Use the Law of Sines.
#5: Use the Law of Cosines.
#6: Use the Pythagorean Identity.
Hey guys! For the life of me I can't figure out how to arrive at the answers provided to exercises #4,5,6 (scan of questions provided below). I don't know which formula to use for which problem. If anyone can help and show the steps used that would be appreciated since this is killing me right now. Thanks a bunch! The answer to #4 is 1/2sin70deg ; the answer to question #5 is square root of 12 ; the answer to question #6 is 12/13