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Thread: trig special rations

  1. #1
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    trig special rations

    hi guys! i need explanation

    how do we solve questions like sin 135, cos 60, tan -180, cos -270 without using calculator.
    Pls explain it to me clearly. thank u
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  2. #2
    Member u2_wa's Avatar
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    Quote Originally Posted by thereddemon View Post
    hi guys! i need explanation

    how do we solve questions like sin 135, cos 60, tan -180, cos -270 without using calculator.
    Pls explain it to me clearly. thank u
    First of all you should remember the basic sine and cosine values:
    $\displaystyle sin(30)=\frac{1}{2}$ , $\displaystyle cos(30)=\frac{\sqrt{3}}{2}
    $

    $\displaystyle sin(45)=\frac{\sqrt{2}}{2}$ ,$\displaystyle cos(45)=\frac{\sqrt{2}}{2}$

    $\displaystyle sin(60)=\frac{\sqrt{3}}{2} $ ,$\displaystyle cos(60)=\frac{1}{2}$

    $\displaystyle sin(135)=sin(90+45)=sin(90).cos(45)+cos(90).sin(45 )$

    $\displaystyle tan(-180)=tan(180)=tan(0)=0$

    $\displaystyle cos(-270)=cos(360+(-270))=cos(90)=0$

    Hope this helps
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