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Math Help - Quick question

  1. #1
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    Quick question

    Can someone explain to me how you can go from
     (\frac{cosx+sinx}{cosx})(\frac{cosx}{1})
    to
     =cosx+sinx

    I thought it would be (sinx)(cosx), so I must not understand something!

    Thanks!
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  2. #2
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    Re: Quick question

    Quote Originally Posted by whit221 View Post
    Can someone explain to me how you can go from
     (\frac{cosx+sinx}{cosx})(\frac{cosx}{1})
    to
     =cosx+sinx

    I thought it would be (sinx)(cosx), so I must not understand something!

    Thanks!
    Do you see that  (\frac{a+b}{c})(\frac{c}{1})=a+b~?
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  3. #3
    MHF Contributor

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    Re: Quick question

    I don't see how you could possibly think that canceling the cos(x) in both numerator and denominator will cause "cos(x) plus sin(x)" to become "cos(x) times sin(x)".
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  4. #4
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    Lexington, MA (USA)
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    Re: Quick question

    Hello, whit221!

    Can someone explain to me how you can go
    . . from \frac{\cos x+\sin x}{\cos x}\cdot\frac{\cos x}{1} to \cos x+\sin x

    I thought it would be \sin x\cos x

    Did you do something really silly?

    . . \frac{{\color{red}\rlap{////}}\cos x + \sin x}{{\color{red}\rlap{////}}{\cos x}}\cdot \dfrac{\cos x}{1} \;=\;\sin x\cos x
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