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Math Help - Basic trig

  1. #1
    Junior Member
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    Basic trig

    I just get confused by something very basic,

    Imagine we got cos 2x = something

    And the angle lies between 0 and 180

    so to solve it, i gotta multiply the range by 2 right ?

    I mean when the equation gets complex, how to do these kind of things...

    Do i solve for 2x first then divide, or find x and find it in its quadrant, sorry, i dont really get it...

    like i had this number sin2x = 1/2

    range was -180 to 180

    so you solve for 2x which gives you 30

    so x = 15 right,

    muliplying the range gives me - 360 to 360

    the answer is 15 75 -165 -105

    can someone explain it to me, im a bit confused...
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  2. #2
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    Quote Originally Posted by ramzel View Post
    I just get confused by something very basic,

    Imagine we got cos 2x = something

    And the angle lies between 0 and 180

    so to solve it, i gotta multiply the range by 2 right ?

    I mean when the equation gets complex, how to do these kind of things...

    Do i solve for 2x first then divide, or find x and find it in its quadrant, sorry, i dont really get it...

    like i had this number sin2x = 1/2

    range was -180 to 180

    so you solve for 2x which gives you 30

    so x = 15 right,

    muliplying the range gives me - 360 to 360

    the answer is 15 75 -165 -105

    can someone explain it to me, im a bit confused...
    \sin(2x) = \frac{1}{2}

    note that the value of 2x must be in quads I and II ...

    -180 < x < 180

    -360 < 2x < 360

    between 0 and 360 ... 2x = 30 \, , \, 150

    x = 15 \, , \, 75

    and between 0 and -360 ...

    2x = -210 \, , \, -330

    x = -105 \, , \, -165
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  3. #3
    Junior Member
    Joined
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    Thank you
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