Please Help!

**jlldbr216** · January 6th 2010, 09:00 AM

I'm trying to figure out this mathbits homework. I don't think I'm getting this particular answer because the URL won't work.

Find the exact value of sinetheta when costheta = 3/5 and the terminal side of theta is in quadrant four

Thanks so much

**adkinsjr** · January 6th 2010, 10:28 AM

Originally Posted by jlldbr216

I'm trying to figure out this mathbits homework. I don't think I'm getting this particular answer because the URL won't work.

Find the exact value of sinetheta when costheta = 3/5 and the terminal side of theta is in quadrant four

Thanks so much

All you need to do is draw a right triangle and solve it. Remember that $cos(\theta)=\frac{adjacent}{hypotenuse}$ . The hypotenuse is 5, the adjacent side is 3, and so the pythagorean theorem gives $x^2=25-9=16$ . So the remaining side is $x=4$ . So sine should be $\pm\frac{4}{5}$ . If the terminal side is in quadrant four, then what is the sign $\pm$ of sine?

$sin(\theta)=-\frac{4}{5}$

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