Originally Posted by

**vaironxxrd** Hello Everyone,

I'm having a little bit of trouble with the following problem.

I need to find $\displaystyle cos(v - u)$ using $\displaystyle sin\ u = \frac{7}{25}, cos\ v = -\frac{3}{5}$

I tried using those values to find the missing functions

$\displaystyle sin\ u = \frac{7}{25}, cos\ u = \frac{24}{25} \ and \ cos\ v = -\frac{3}{5}, sin\ v = \frac{4}{5}$

Then i used the following formula ...$\displaystyle cos(v - u) = cos\ v \cdot cos\ u + sin\ v \cdot sin\ u$ Replaced the numbers

$\displaystyle -\frac{3}{5} \cdot \frac{24}{25} + \frac{4}{5} \cdot \frac{7}{25}$

=

$\displaystyle -\frac{44}{175}$