trig

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I'm confused with this concept:

Okay, so I have this problem:

cos2x( 2 cos+1)= 0

I understand I have to work the problems separately and I get cos x= 2 and cos x= 1/2

Now, what I don't understand is how this connects to pi, radians or the unit circle. If someone could explain or point me to a place with a thorough explanation, please tell me. B/c trust me, I've looked EVERYWHERE and my book/teacher doesn't really explain the theory very well.

  • trig -

    I get cos x= 2 ?????
    I do not
    I get
    cos 2 x = 0
    that means that 2x = pi/2 or 90 degrees or 2x = 3 pi/2 or 270 degrees
    or x = pi/4 or 3pi/4
    then
    cos x = -1/2
    well cos of 60 degrees or pi/3 is 1/2
    so cos (180-60) = -1/2 so x =2pi/3
    or 180+60 which is 5pi/3

  • trig -

    sry it's cos^2x

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