Question 984824
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You should get used to using radians instead of degrees. *[tex \Large 90^\circ\ =\ \frac{\pi}{2}] 


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \ \cos\left(x\ +\ \frac{\pi}{2}\right)\ =\ 2\sin^2x]


*[tex \LARGE \ \ \ \ \ \ \ \ \ -\sin(x)\ =\ 2\sin^2x]


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \ \sin(x)\ =\ -\frac{1}{2}]


Use the unit circle to find the angle whose sine is negative 1/2 in the given interval.  Negative angles are measured clockwise from the positive x-axis.


 *[illustration unit_circle]


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it

*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \