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September 23, 2014

September 23, 2014

Posted by **Anonymous** on Thursday, November 22, 2007 at 5:35pm.

0 less than and/or equal to "x" less than and/or equal to 360

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cos^2x - 1 = sin^2x

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Attempt:

cos^2x - 1 - sin^2x = 0

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

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

2cos^2x - 2 = 0

(2cos^2x/2)= (-2/2)

cos^2x = -1

cosx = square root of -1

And I can't do anything with this now...what am I doing wrong?

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Textbook answers:

0, 180, 360

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- Math - Solving for Trig Equations -
**bobpursley**, Thursday, November 22, 2007 at 5:40pmOn the fourth/fifth line, you erred. When you add 2 to both sides, the right side is positive, not negative.

cos^2 x=1

cos x= +- 1

giving 1, 180,360

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