SOLUTION: Suppose there is an angle theta where pi/2 <= theta <= pi. Also, sin theta = a. Find cos theta in terms of a.

Question 904342: Suppose there is an angle theta where pi/2 <= theta <= pi. Also, sin theta = a. Find cos theta in terms of a.
Found 2 solutions by lwsshak3, KMST:
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
Suppose there is an angle theta where pi/2 <= theta <= pi. Also, sin theta = a. Find cos theta in terms of a.
use x for theta
reference angle x is in quadrant II where sin>0, cos<0
sin(x)=a
cos^2(x)+sin^2(x)=1
cos(x)=-√(1-sin^2(x))=-√(1-a^2)

Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
An angle such that is in quadrant II (or its borders),
where sine is positive (or zero), and cosine is negative (or zero), so .
We know that , so if ,
then ---> ,
and since , it must be
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