SOLUTION: Find all solutions to the equation. cos x = -1/2

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Question 732671: Find all solutions to the equation.
cos x = -1/2
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
We know that cos%2860%5Eo%29=1%2F2 (or cos%28pi%2F3%29=1%2F2 if measuring angles in radians).
Negative cosines happen only in the second and third quadrants.
cos%28180%5Eo-60%5Eo%29=cos%28120%5Eo%29+=-cos%2860%5Eo%29=-1%2F2
(or cos%28pi-pi%2F3%29=cos%282pi%2F3%29=-cos%28pi%2F3%29=-1%2F2 in radians) shows us one of the solutions.
An angle with the same cosine in the third quadrant is -120%5Eo (or -2pi%2F3 in radians and that is another solution.
The other solutions are all angles coterminal with those two angles.
They can all be expressed as
360%5Eo+%2B-+k%2A120%5Eo or 2pi+%2B-+2k%2Api%2F3 for any integer k.