Posted by **Nan** on Friday, December 29, 2006 at 4:24pm.

Given:

cos u = 3/5; 0 < u < pi/2

cos v = 5/13; 3pi/2 < v < 2pi

Find:

sin (v + u)

cos (v - u)

tan (v + u)

First compute or list the cosine and sine of both u and v.

Then use the combination rules

sin (v + u) = sin u cos v + cos v sin u.

cos (v - u) = cos u cos v + sin u sin v

and

tan (u + v) = [tan u + tan v]/[1 - tan u tan v]

We got sin u = 4/5 & sin v = SQRT (7/13)

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