The value at angle pie/4 and at -pie/4 is equal from y =3 ..therefore equatn of axis of symmetry y=3..i.e C=3
period or range for 1 cycle is 180..use 180/b...so b=1
amplitude i.e height from axis of symmetry in either directn so 5-3=2, 3-1=2..therefore a=2