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# Further Trigonometry watch

1. Really need help with a couple of trig questions, I hope someone can help me. Thank you so much in advance!!!

the angles x and y are acute and x is greater than y. Given that cosxcosy=1/4 and sinxsiny=1/4, find the values of cos(x+y) and cos(x-y) and hence find the values of x and y
2. Well, first of all cos (x + y) = cos x.cos y - sin x.sin y and cos (x - y) = cos x.cos y + sin x.sin y.
3. So, cos(x+y)= 1/4 - 1/4 = 0 and cos(x-y)= 1/4 + 1/4 = 2/4 = 1/2, right?
We now know that
cos(x+y)=0 and
cos(x-y)= 1/2.

4. (Original post by Leen!)
So, cos(x+y)= 1/4 - 1/4 = 0 and cos(x-y)= 1/4 + 1/4 = 2/4 = 1/2, right?
We now know that
cos(x+y)=0 and
cos(x-y)= 1/2.

I got up to there but I'm not sure how to solve cos(x-y)=1/2 :/
-missing lessons is not a good idea lol
5. (Original post by Lavanyaa)
I got up to there but I'm not sure how to solve cos(x-y)=1/2 :/
-missing lessons is not a good idea lol
Well what values of A do you know that satisfy cos A = 1/2?
6. (Original post by davros)
Well what values of A do you know that satisfy cos A = 1/2?
60 & 300?

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