14 To answer questions 12 17 use the formulas for functions of the differen and sum of two angles to find without tables or calculator the cosine si and tangent of the angle 15 using 45 and 30 cos 15 A cos 45 cos 30 sin 45 sin 30 sin 45 cos 30 cos 45 sin 30 OC cos 45 cos 30 sin 45 sin 30 OD sin 45 cos 30 cos 45 sin 30 B