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December 20, 2014

December 20, 2014

Posted by **anna** on Saturday, November 1, 2008 at 2:54am.

inverse sin (-rad2/2)=-45 degrees

I dont understand why cos is 135

- trig -
**Damon**, Saturday, November 1, 2008 at 10:40amfor the cosine = -sqrt 2/2 negative x axis

means quadrant 2 or quadrant 3

It could be either 180 + 45 or 180 - 45

so either 135 or 225

for the sine = -sqrt 2/2

means quadrant 3 or quadrant 4

that is 180 + 45 or 360 - 45

so either 225 or 315

225 satisfies both the sine and the cosine.

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