Given sinx=4/5, cosy = 7/25. Find the following

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Homework Statement



Angles x and y are located in the first quadrant such that sinx=4/5, and cosy = 7/25.

a) Determine an exact value of cosx.

b) Determine an exact value of siny.

c) Determine an exact value for sin(x+y)


Homework Equations



Compound angle formulas perhaps? I don't really know, that's the problem!

The Attempt at a Solution



I'm really at a loss here, do I just sub those into some formula or something? Can anyone help me out? Or get me pointed in the right direction? thanks in advance!
 
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Let's start with part a). Have you thought about sin^2(x) + cos^2(x) = 1?
 
Holy smoke I can't believe I missed that! thanks hitman! I owe you one!

Now for the last 2 lil buggers!
 
well I got a and b, now how would I do c? :|
 
Nevermind, I got it, thanks for your help hitman! I don't know how on Earth i missed that!
 
sin(x+y) = sinx*cosy+siny*cosx
 

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