SOLUTION: sin u = −5/13 and cos v = −15/17 (Both u and v are in Quadrant III.) what is cos(u+v)

Question 1147426: sin u = −5/13
and
cos v = −15/17
(Both u and v are in Quadrant III.)
what is cos(u+v)
Found 2 solutions by greenestamps, ikleyn:
Answer by greenestamps(13203) (Show Source): You can put this solution on YOUR website!

5-12-13 and 8-15-17 are Pythagorean Triples. So

sin u = -5/13 in quadrant III --> cos u = -12/13
cos v = -15/17 in quadrant III --> sin v = -8/17

Then

Use a calculator....
Answer by ikleyn(52835) (Show Source): You can put this solution on YOUR website!
.

This problem IS NOT about getting "the value". It is about getting the answer in the form of a fraction. So, you need substitute the fractions into the formula and calculate and present the answer as a fraction. cos(u+v) = cos(u)*cos(v) - sin(u)*sin(v) = = = = . ANSWER It is THE expected form of the solution and the answer to this problem.

Solved.

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