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

  • Thread starter Thread starter Random-Hero-
  • Start date Start date
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
5 replies · 5K views
Random-Hero-
Messages
40
Reaction score
0

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!
 

Discussion

Physics news on Phys.org
Let's start with part a). Have you thought about [tex]sin^2(x) + cos^2(x) = 1[/tex]?
 
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