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Math Help - Identity conundrum

  1. #1
    Junior Member
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    Exclamation Identity conundrum

    Having troubles proving the identity
    tanx/secx+1 = 2cosx-2cosx^2x/sin2x
    Thanks
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  2. #2
    Master Of Puppets
    pickslides's Avatar
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    What have you tried?

    Does this help?

    \frac{\tan x}{\sec x+1}\times \frac{\sec x-1}{\sec x-1}=  \frac{\tan x (\sec x-1)}{\sec^2 x-1}=  \frac{\tan x (\sec x-1)}{\tan^2 x}
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  3. #3
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    still having troubles
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  4. #4
    Lord of certain Rings
    Isomorphism's Avatar
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    Now, does this help?

    \frac{\tan x (\sec x-1)}{\tan^2 x} = \frac{\cos x(\sec x-1)}{\sin x} = \frac{2\cos^2 x(\sec x-1)}{2\cos x \sin x} = \frac{2\cos^2 x\sec x - 2\cos^2 x}{\sin 2x}
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