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Math Help - Simultaneous equation with cos or sin

  1. #1
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    Simultaneous equation with cos or sin

    Find P and Q


    <br />
Pcos20-Qcos50=16cos45<br />
    <br />
Psin20+Qsin50=16sin45<br /> <br />

    what i did was find P which =

    <br /> <br />
(16cos45+Qcos50)/cos20<br /> <br />

    then sub that in the first equation.

    so it would be [16cos45+Qcos50-Qcos50=16cos45]

    but that's not going to find Q

    Any help is appreciated!
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  2. #2
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    Quote Originally Posted by BabyMilo View Post
    Find P and Q


    <br />
Pcos20-Qcos50=16cos45<br />
    <br />
Psin20+Qsin50=16sin45<br /> <br />

    what i did was find P which =

    <br /> <br />
(16cos45+Qcos50)/cos20<br /> <br />

    then sub that in the first equation.

    try substituting it into the 2nd equation instead
    ...
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  3. #3
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    lol i realise that but still cant do it really!
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  4. #4
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    Quote Originally Posted by BabyMilo View Post
    lol i realise that but still cant do it really!
    why not?

    \frac{16\cos(45)+Q\cos(50)}{\cos(20)} \cdot \sin(20) + Q\sin(50) = 16\sin(45)<br />

    multiply by \cos(20) to clear the fraction ...

    [16\cos(45)+Q\cos(50)] \sin(20) + Q\sin(50)\cos(20) = 16\sin(45)\cos(20)

    finish up by isolating Q
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  5. #5
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    thanks! although worked it out before your post!
    thanks though! hehe!
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