Posted by **pete** on Tuesday, July 21, 2009 at 3:35pm.

if sin(theta)=1/4

and pie/2<theta<pie what is the value of cos(theta)

- math -
**Reiny**, Tuesday, July 21, 2009 at 4:48pm
make a rough sketch of a right-angled triangle in the second quadrant with a hypotenuse of 4 and a vertical leg of 1.

(remember sin(angle) = opposite/hypotenuse)

by Pythagoras, the other side must be √15

in the second quadrant the cosine is negative, so

cos(theta) = -√15/4

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