Question

cos(x-y) when cosx=3/5 and cos y=4/5
Last problem before I don't understand. Exam in four hours =/ Please help :D

Answer 1

You're supposed to find the exact value. Cos(x-y)=cosx cosy + sinx siny

Answer 2

cosx=3/5 >>>cos^2x=(9/25)
sin^2x+cos^2x=1>>>>
sin^2x=1-cos^2x>>> sinx = 4/5 >>>>>> on the sameway you can found sin y go on ,

cosx=cosx*cosy+sinx siny
>>>

Answer 3

get it