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Hannah_Ahn

  • 4 years ago

prove the identity: \[\cos x + \sin x \tan x \over \sin x \sec x \] = csc x

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  1. Yifan12879
    • 4 years ago
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    LHS=(cosx +sinx tanx)*cosx / sinx secx cosx =(cos^2 x +sin^2 x) / sinx =1/sinx=cscx

  2. Yifan12879
    • 4 years ago
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    i think this one is easier to understand :)

  3. Hannah_Ahn
    • 4 years ago
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    I don't understand, I feel so dumb.. why did you multiply deno and numerators by cos x and how you've got cos^2x+sin^2x over sinx

  4. Yifan12879
    • 4 years ago
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    because tanx cosx=sinx, secx cosx=1 multiply cos x makes LHS simpler

  5. myininaya
    • 4 years ago
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    \[\frac{\cos(x)+\sin(x) \cdot \frac{\sin(x)}{\cos(x)}}{\sin(x) \cdot \frac{1}{ \cos(x)}} \cdot \frac{\cos(x)}{\cos(x)}=\frac{\cos^2(x)+\sin^2(x)}{\sin(x) }=\frac{1}{\sin(x)}=\csc(x)\] This is exactly what Yifan did, but I think it looks better in latex ;) Good work Yifan

  6. Hannah_Ahn
    • 4 years ago
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    Yifian: woot that was so simple! thanks! haha thanks myinninaya :)

  7. Yifan12879
    • 4 years ago
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    when you meet tanx secx cscx, substitute them with sinx/cosx, 1/cosx, 1/sinx, to make the problem simpler:)

  8. Hannah_Ahn
    • 4 years ago
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    got it (:

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