I need to find the exact value of the trigonometric function

PlsHelp

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Oct 21, 2015
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I've tried figuring this out but i'm not getting it at all.

Find cos(
α + β) given that

sin
α = 4/5 , 0 < α , π/2; cosβ = 7/25, 0 < β < π/2
 
I've tried figuring this out but i'm not getting it at all.

Find cos(
Calculate the value of cos(α + β) given that

sin
α = 4/5 , 0 < α , π/2; cosβ = 7/25, 0 < β < π/2

Hint:

cos(α + ß) = cos(α) * cos(ß) - sin(α) * sin(ß)

and

sin2(A) + cos2(A) = 1
 
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