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C3 Trig Help! watch

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    sin2x = cos2x, solve for 0<x<2pi

    i have tried rearranging and all i get is: 2sin^2x -2sinxcosx -1 = 0, and that doesn't factorise.

    Please point me in the right direction

    thanks (oh and rep on offer, altho it wont be worth much =P )
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    I'd put sin 2x - cos2x in R sin (2x + alpha ) form
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    I would divide both sides by cos 2x to give you tan 2x = 1, then solve from there?
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    2sinxcosx = cos2x - sin2x

    Divide through by cos2x

    2tanx = 1 - tan2x

    And make a quadratic out of that
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    (Original post by LetoKynes)
    I would divide both sides by cos 2x to give you tan 2x = 1, then solve from there?
    This.
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    ah cheers guys. you guys make c3 seem look so simple lol
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    :facepalm: Why didn't I see that :hmmm:
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    (Original post by Tommy Jay)
    ah cheers guys. you guys make c3 seem look so simple lol
    Trig is a nasty chapter, because even if you do understand it, you might not see the solution. What I've worked out when doing trig is that most of the time when proving something you should look out for these things.

    -Sin and cos turning into tan
    -sin^2 + cos^2 = 1
    -1 + tan^2 = Sec^2
    -1 + cos^2 = Cot^2
    -Cos 2x giving cos^2 x-sin^2 x which is the difference of two squares, (cosx+sinx) (cosx-sinx)
    -Then ofc just expanding sin 2x and cos 2x normally

    Just look out for these in that order, they are usually the trickiest
 
 
 
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Updated: January 31, 2010

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