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January 30, 2015

January 30, 2015

Posted by **stellar** on Saturday, October 22, 2011 at 12:37am.

2 cos2 θ − cos θ − 1 = 0

- precal -
**Steve**, Saturday, October 22, 2011 at 6:38amwhat's the problem. You know how to solve quadratics:

Let x = cosθ

2x^2 - x - 1 = 0

(2x+1)(x-1) = 0

x = -1/2 or 1

So,

cosθ = -1/2 or 1

. . .

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