If A and B are second quadrant angles such that cos A = -2/5 and sin B = 3/7, find the exact value of sin (A-B). Express your answer as one fraction; you do not need to rationalize.

Question

mertsj · Answer

$$\sin(A-B)=sinAcosB-cosAsinB$$

anonymous · Answer

you still have to find $\sin(B)$ and $\cos(A)$ to finish this
do  you know how to do that?

anonymous · Answer

Yes, but plugging in the values into the equation would not give a final fraction, right? My teacher wants me to have in answer in fraction form.

anonymous · Answer

Okay never mind, I don't know what I'm doing now.

mertsj · Answer

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