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Math Help - how to calculate this ... some algebra rule?

  1. #1
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    Unhappy how to calculate this ... some algebra rule?

    guys if I have something like this:

    cos(theta)/x=r can I transpose this fomula as x=r*cos(theta) - is this correct?

    btw. I am trying to understand if x-adjacent r-hypothenus x=r*cos(theta) -> I want to come up to this part while taking into consideration that cos(theta)=x/r

    please help me
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  2. #2
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    e^(i*pi)'s Avatar
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    edit: my bad,misread

    Taken at face value if r = \dfrac{\cos \theta }{x} \text{  then  } x = \dfrac{\cos \theta}{r}


    I suspect you want to show, using a right angled triangle that x = r \cos \theta.

    If this is the case recall that by definition \cos \theta = \dfrac{\text{adjacent}}{\text{hypotenuse}}
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  3. #3
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    could you please show me how to go step-by-step from: \cos \theta = \dfrac{\text{x}}{\text{r}}
    to x = r \cos \theta -> transpose formulae step is very important for me ... to understand what I look for
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  4. #4
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    e^(i*pi)'s Avatar
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    Multiply both sides by r

    r \cos \theta = \dfrac{x}{r} \cdot r = x
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