Find the exact value of the expression using the provided in

Find the exact value of the expression using the provided information. Find cos(s-t) given that cos s = -3/5, with s in quadrant II, and cost = 5/13, with t in quadrant IV. 33/65 63/65 -63/65 -33/65

Solution

cost = 5/13

t is in IVrth quadrant

sint = -12/13

cos = -3/5 s is in IIn quadrant

sins = 4/5

cos( s-t) = cosscost +sinssint = (-3/5)(5/13) + (-12/13)(4/5)

= (--15 --48)/65

= -63/65