Question 653374
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*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \cos^{-1}\left(0\right)]


means "The angle whose cosine is zero".


Use the unit circle to find all angles for which the cosine is zero.  Hint:  The cosine of an angle is equal to the *[tex \LARGE x]-coordinate of the point where the terminal ray of the angle intersects the unit circle.


<img src="http://www.math.ucsd.edu/~jarmel/math4c/Unit_Circle_Angles.png">


Note:  Unless you specify a more restricted range for your inverse cosine function, any angle *[tex \LARGE \varphi] is equivalent to *[tex \LARGE \varphi\ +\ 2\pi]


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