I need to find the exact value of the trigonometric function

[PlsHelp]

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

Find cos(

α + β) given that

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

 

[Deleted member 4993]

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

sinα = 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