Matthew G.

asked • 01/25/22

If x and y are angles in the second quadrant such that sin (x) = 2/9 and cos (x) = -4/5 determine the exact value of sin (x+y)

Aaron W.

You have written sin x and cos x. One of these must be y rather than x. sin(x + y) = sin(x) cos(y) + sin(y) cos(x) then you know that cos^2(x) + sin^2(x) = 1. You can use this for both x and y cases to find the other function. e.g. If you have cos(x), you can find exact value of sin(x) In the 2nd quadrant, we know that the sine if positive and cosine is negative. This information must also be used. So, you can then solve for exact solution.
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01/29/22

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