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Math Help - Proving Identities

  1. #1
    Newbie
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    Apr 2005
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    Proving Identities

    I am having problems with proving identities. Could someone please help me?

    1. tanx + cot x = secxcscx

    2. sec^2x = ___cscx____
    cscx - sinx

    3. _tan^2t__ = sect - cost
    sect
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  2. #2
    Junior Member
    Joined
    Apr 2005
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    We first need to know these three facts,

    tan x = sin x / cos x
    cotan x = cos x / sin x
    (sin x)^2 + (cos x)^2 = 1
    Then,
    tan x + cotan x = (sin x / cos x) + (cos x / sin x)
    = ((sin x)^2 + (cos x)^2)/(sin x * cos x)
    = 1 / (sin x * cos x)
    = (1/sin x)*(1/cos x)
    = csc x sec x = sec x csc x

    Get the idea now? When dealing with sec x and csc x it is usually easier to put them in terms of sine and cosine and just grind through the algebra.
    Last edited by beepnoodle; April 18th 2005 at 06:19 PM.
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