Posted by **House** on Friday, October 3, 2008 at 1:02pm.

If 0<theta<90 and tan theta= (square root 3)/2, find cos theta?

tan(t) =ã3 /2; cos(t) = 1/ã(1+(tant)^2)= 1/ã(1+3/4) = 2/ã7

right or wrong?

- Math -
**Reiny**, Friday, October 3, 2008 at 4:45pm
You are doing this the hard way.

make a diagram

since tan theta = √3/2, and tan theta = opposite/adjacent, make the oppose √3 and the adjacent 2

In your head you could do Pythagoras and get the hypotenuse √7

since cos theta = adjacent/hypotenuse

cos theta = 2/√7

which is what you got.

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