anonymous 3 years ago Given: a and B are first-quadrant angles, sin a=5/13, and cosB= 3/5. evaluate sin(a-B). a.) -33/65 b.) 33/65 c.) 63/65

1. ash2326

Use this here $\sin (A-B)=\sin A\times \cos B-\sin B\times \cos A$

2. ash2326

sin a=5/13, and cosB= 3/5

3. anonymous

I tried this but the book is asking me to subtitute pi/2 for a

4. anonymous

and I know I have to solve for sin B and cos A

5. ash2326

$\sin (B)=\cos (\frac {\pi}{2} -B)$ $\cos A=\sin (\frac{\pi}{2}-{A})$ you can use $\sin^2 x+\cos^2 x=1$ to figure out sin B and cos A

6. anonymous

ok ill try this

7. anonymous

cos a= 12/13

8. ash2326

correct :)