Question 918190
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The coordinates of any point on a unit circle are related in either of the following fashions:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ P\left(x,\,\pm\sqrt{1\,-\,x^2}\right)]


or


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ P\left(\pm\sqrt{1\,-\,y^2},\,y\right)]


Which follows directly from Pythagoras.  Since you are given the *[tex \Large x] coordinate, use the first one.  Select the sign based on the sign of the desired coordinate that is correct for the given quadrant.


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

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