Im stuck on 2 problems:

1. cos2x(2cos+1) (I dont know even where to start)

and

tan3x=1this one im beter off on

i relize that tan=1 on (pie/4)

diveded by three for the three rotations you get (pie/12)

i know the answers are (pie/12 + pie N) the book says they are (pie/12, 9pie/12, 17pie/12, 5pie/12, 13pie/12, 21pie /12) how did it get these

thanks