SOLUTION: Find the exact value of the trigonometric expression when sin(u) = − 5/13 and cos(v) = − 4/5. (Both u and v are in Quadrant III.) cos(u + v)

Question 1172168: Find the exact value of the trigonometric expression when sin(u) = − 5/13 and
cos(v) = − 4/5. (Both u and v are in Quadrant III.)
cos(u + v)
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Half angle formulas on Wikipedia covers this very well.
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What is the point of having someone do them for you?
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PS There are a LOT of formulas. I remember some of them, but not all.
There's no good reason to try to memorize all of them, and I doubt that anyone can.

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