Question 334343
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Take a look at the unit circle:


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


In the unit circle, the *[tex \LARGE x]-coordinate represents the value of cosine.


Since you didn't specify an interval for *[tex \LARGE \theta],


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \theta\ =\ \frac{3\pi}{4}\ +\ 2k\pi]


or


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ \theta\ =\ \frac{5\pi}{4}\ +\ 2k\pi]


where *[tex \LARGE k\ \in\ \mathbb{Z}]


John
*[tex \LARGE e^{i\pi} + 1 = 0]
My calculator said it, I believe it, that settles it
<img src="http://c0rk.blogs.com/gr0undzer0/darwin-fish.jpg">
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