12. a) Determine an exact value for sin 17\" 12 b) Determine the answer to part a) using a different method. 13 . Angle x is in the second quadrant and angle 3/ is in the rst quadrant such that sinx = % _ i and cosy 13 . a) Determine an exact value for cos x. b) Determine an exact value for sin y. t) Determine an exact value for cos(x y)