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## Homework Statement

Angle

*a*is located in the second quadrant where sin

*a*=2/5 and angle

*b*is located in the third quadrant where tan

*b*=3/4. Determine an exact value for cos(

*a+b*) and where it is located.

## Homework Equations

cos(a+b)=cosacosb+sinasinb

## The Attempt at a Solution

I don't know what I'm doing