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Math Help - trig identity help...

  1. #1
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    trig identity help...

    I can't solve this :S

    cosxsinx/tanx = 1 - sin^2x

    thanks
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  2. #2
    Behold, the power of SARDINES!
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    Quote Originally Posted by katiethegreat View Post
    I can't solve this :S

    cosxsinx/tanx = 1 - sin^2x

    thanks
    Hint:

    \frac{\cos(x)\sin(x)}{\tan(x)}=\frac{\cos(x)\sin(x  )}{1}\cdot \frac{\cos(x)}{\sin(x)}=...
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  3. #3
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    I don't know why....but i still don't get it :/
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  4. #4
    Behold, the power of SARDINES!
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    Quote Originally Posted by katiethegreat View Post
    I don't know why....but i still don't get it :/
    what is "it" you don't understand how I change what you had into this

    \frac{\cos(x)\sin(x)}{\tan(x)}=\frac{\cos(x)\sin(x  )}{1}\cdot \frac{\cos(x)}{\sin(x)}=...

    or you don't know how to finish the problem. Where are you stuck?
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  5. #5
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    both :/
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  6. #6
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    Hi katiethegreat,

    Maybe if you see it like this, it would help:

    \dfrac{\cos (x) \sin(x)}{\tan (x)}=

    \dfrac{\cos(x) \sin(x)}{\frac{\sin (x)}{\cos (x)}}=

    \dfrac{\cos (x) \sin (x)}{1} \cdot \frac{\cos (x)}{\sin (x)}=

    He just used the identity: \tan (x) = \frac{\sin (x)}{\cos (x)}

    You should be able to finish now if you know \sin^2(x)+\cos^2(x)=1


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