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Math Help - i want to explain the solution in this question

  1. #1
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    i want to explain the solution in this question

    i want to explain the solution in this question ..
    I worked a red line on the steps that I did not understood it
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by r-soy View Post
    i want to explain the solution in this question ..



    I worked a red line on the steps that I did not understood it
    Hi r-soy,

    \cos \frac{3\pi}{2}=0

    \sin \frac{3\pi}{2}=-1

    Does that help?
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  3. #3
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    Hi but from where we get
    <br />
\cos \frac{2\pi}{2}<br />
    in step 2
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  4. #4
    A riddle wrapped in an enigma
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    Quote Originally Posted by r-soy View Post
    Hi but from where we get
    <br />
\cos \frac{2\pi}{2}<br />
    in step 2
    Looks like it might be a mistake to me. Should be \cos \frac{3\pi}{2}
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  5. #5
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    thanks so much
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  6. #6
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    ok who u can know

    cos(3pi/2)=cos(270)=0
    sin(3pi/2)=sin(270)= -1

    from where i can get 0 and -1 ?

    give me a way to finid them
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  7. #7
    A riddle wrapped in an enigma
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    Quote Originally Posted by r-soy View Post
    ok who u can know

    cos(3pi/2)=cos(270)=0
    sin(3pi/2)=sin(270)= -1

    from where i can get 0 and -1 ?

    give me a way to finid them
    On your unit circle, at an angle of 270 deg or 3pi/2, the coordinates of the intersection of the circle with the negative side of the y-axis is (0, -1). Cosine is defined as x/r, where x = x-coordinate of the circle and r = the radius.

    \cos 270=\frac{x}{r}=\frac{-1}{1}=-1

    Similarly, sine 270 is defined as y/r.

    \sin 270=\frac{y}{r}=\frac{0}{1}=0

    Print this image and study it: Unit Circle
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