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January 30, 2015

January 30, 2015

Posted by **Megan** on Thursday, August 27, 2009 at 10:31am.

cos2x=(*2/2)

- MEGAN !! Pre Calc -
**Reiny**, Thursday, August 27, 2009 at 12:20pmMegan, look at how your post came out.

what is *2/2 supposed to be?

I have a feeling you mean √2/2

If so, then

since the cosine is positive in quadrants I and IV

2x = 45º or 2x = 315º

then x = 22.5º or x = 157.5º

but we know that the period of cos(2x) is 180º, so by adding 180 to each of our answers we get the other solutions in the given domain, or

x = 202.5º

x = 337.5º

just noticed that you probably wanted the solutions in radians, that would be

pi/8, 7pi/8, 9pi/8, and 15pi/8

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