# Trig functions

• Jun 2nd 2005, 07:30 AM
cassie
Trig functions
If sin^2 of theta = 1/2 and pi< theta < 3pi/2 (quadrant III) then theta= ?

I have no idea how to do these type of problems! Please Help!
• Jun 2nd 2005, 08:09 AM
$
\sin^2 \theta = \frac {1} {2}
\Rightarrow \sin \theta= \frac {1}{\sqrt{2}}

\Rightarrow \theta= -\frac {\pi} {4}

\Rightarrow \theta= \pi + \frac{\pi}{4}

\Rightarrow \theta= 5\frac{\pi}{4}
$
• Jul 11th 2005, 10:38 PM
vms
Quote:

Originally Posted by askmemath
$
\sin^2 \theta = \frac {1} {2}
\Rightarrow \sin \theta= \frac {1}{\sqrt{2}}

\Rightarrow \theta= -\frac {\pi} {4}

\Rightarrow \theta= \pi + \frac{\pi}{4}

\Rightarrow \theta= 5\frac{\pi}{4}
$

sine of theta must be taken as negative sqaure root of half here.
then the value of theta will be 5Pi/4