How do you find the exact value #cos(x-y)# if #cosx=3/5,cosy=4/5#?
1 Answer
Dec 17, 2016
Explanation:
Use trig identity:
cos (x - y) = cos x.cos y + sin x.sin y
We have cos x = 3/5, find sin x
We have cos y = 4/5, find sin y
Since cos x > 0 and cos y > 0, then the arcs x and y are both located in Quadrant I. Their sin are both positive. There for: