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January 29, 2015

January 29, 2015

Posted by **Dre** on Sunday, November 13, 2011 at 4:53pm.

1-cos theta/ sin theta = sqr3, 0degrees <or equal to theta < 369 degrees

cos4x + cos 2x =0, 0<or equal to x < pi

- Math/trig -
**Steve**, Monday, November 14, 2011 at 10:53amRecall that

1-cos theta/ sin theta = tan(theta/2)

so, we want tan(theta/2) = sqrt(3)

theta/2 = 60

theta = 120

Note that theta/2 = 240 also works, but that requires theta=480, outside the domain given.

___________________________

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

(2cos2x - 1)(cos2x + 1) = 0

cos2x = 1/2, so 2x = 60,300, so x=30,150

cos2x = -1, so 2x = 180, so x=90

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