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October 20, 2014

October 20, 2014

Posted by **Diana** on Monday, January 11, 2010 at 11:22pm.

1/ 1+tan^2x = -cos x

How would i do this? im thinking of maybe changing the 1+tan to sec^2x?

- Math -
**drwls**, Tuesday, January 12, 2010 at 1:27amGood idea. Use 1+tan^2 x = sec^2x

Then

1/(1+tan^2x) = -cos x

becomes

1/sec^2x = -cosx

cos^2x + cosx = 0

cosx (cosx + 1) = 0

cos x = 0 or -1

x = pi/2, 3 pi/2 or pi

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