SOLUTION: If α and β are acute angles such that cos α = 4/5 and tan β = 15/8, find the following. a). sin (a+B) b). cos (a+B) I am not sure how to start this. If you know how to d

Question 1158676: If α and β are acute angles such that cos α = 4/5 and tan β = 15/8, find the following.
a). sin (a+B)
b). cos (a+B)
I am not sure how to start this. If you know how to do this please show me the process. I want know how to do this! Thank you.
Answer by MathLover1(20849) (Show Source): You can put this solution on YOUR website!

If and are acute angles such that and , find the following:

a).

given:

find using identity ,then
..........

use given
to find and
since

opposite side=>
adjacent side=>
hypotenuse=>
then

so, we now have

and we can calculate using identity

b). using identity

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