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Thread: Trig

  1. #1
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    Trig

    Can somebody help me do these please.o (greater or equal to) y and (less than or equal to) 360 degrees.

    1. sin(x/2)= √3/2

    2. 2sin^2(x) - 7sin(x) = -3 when o (greater or equal to) x and (less than or equal to) 360 degrees.

    3. and most importantly sin2(y)= 4y when o (greater or equal to) y and (less than or equal to) 360 degrees.

    Thanks.


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  2. #2
    Member Last_Singularity's Avatar
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    Quote Originally Posted by alpina View Post
    Can somebody help me do these please.o (greater or equal to) y and (less than or equal to) 360 degrees.

    1. sin(x/2)= √3/2

    2. 2sin^2(x) - 7sin(x) = -3 when o (greater or equal to) x and (less than or equal to) 360 degrees.

    3. and most importantly sin2(y)= 4y when o (greater or equal to) y and (less than or equal to) 360 degrees.

    Thanks.
    1. Let $\displaystyle y = \frac{x}{2}$. So you're solving
    $\displaystyle sin(y) = \sqrt{3}/2$. Find the value of $\displaystyle y$ and then convert it back to $\displaystyle x$

    2. Let $\displaystyle sin(x) = y$. So you're solving
    $\displaystyle 2y^2 - 7y + 3 = 0$. Solve that for $\displaystyle y$ and then solve the equation $\displaystyle sin(x) = y$

    3. I can't read your notation here. Is it $\displaystyle sin(2y)$ or $\displaystyle sin^2 y$?
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  3. #3
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    Quote Originally Posted by Last_Singularity View Post
    1. Let $\displaystyle y = \frac{x}{2}$. So you're solving
    $\displaystyle sin(y) = \sqrt{3}/2$. Find the value of $\displaystyle y$ and then convert it back to $\displaystyle x$

    2. Let $\displaystyle sin(x) = y$. So you're solving
    $\displaystyle 2y^2 - 7y + 3 = 0$. Solve that for $\displaystyle y$ and then solve the equation $\displaystyle sin(x) = y$

    3. I can't read your notation here. Is it $\displaystyle sin(2y)$ or $\displaystyle sin^2 y$?
    thanks for your reply, and it is $\displaystyle sin(2y)$. first time doing math on computer =)), sorry.
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  4. #4
    Member Last_Singularity's Avatar
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    So for $\displaystyle sin(2y)= 4y$, let $\displaystyle x=2y$. Then we get:
    $\displaystyle sin(x) = 2x$

    Use a graphing calculator of some sorts to find where $\displaystyle sin(x) - 2x = 0$

    Then divide by 2 to get your value of $\displaystyle y$
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  5. #5
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    still don't really understand how to do it right
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