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-   -   Verifying Trig Identities (https://www.askmehelpdesk.com/showthread.php?t=719017)

  • Nov 25, 2012, 12:00 PM
    JackieF
    Verifying Trig Identities
    [sec(A) + csc(A)] ÷ [1+ tan(A)]= csc(A)
  • Nov 25, 2012, 08:56 PM
    RPVega
    Recall the following trig definitions:

    sec(A) = 1 / cos(A);
    csc(A) = 1 / sin(A);
    tan(A) = [sin(A) / cos(A)];
    1 = [sin(A) / sin(A)]

    Substituting the definitions of sec(A), csc(A), and tan(A), in terms of sin(A)
    and cos(A), we have the following:

    [sec(A) + csc(A)] / [ 1 + tan(A)] =

    { [1 / cos(A)] + [1 / sin(A)] } / { [sin(A) / sin(A)] + [sin(A) / cos(A)] }
    The right side of the above equation becomes:

    { [ sin(A) + cos(A) ] / sin(A)cos(A) } / { sin(A)cos(A) + [sin(A)]^2 / sin(A)cos(A) }

    Inverting and multiplying the denominator of the above equation, results in:

    { [ sin(A) + cos(A) ] / [sin(A)cos(A)] } x { sin(A)cos(A) / [sin(A)] ^ 2 + sin(A)cos(A)}

    The term sin(A)cos(A) cancels out of the above equation, and we have:

    [sin(A) + cos(A)] / { [sin(A)] ^ 2 + [sin(A)cos(A)] }

    Factoring sin(A) out of the denominator of the above equation, we have:

    [sin(A) + cos(A)] / { sin(A) [ sin(A) + cos(A)] }

    The sum sin(A) + cos(A) cancels out of the numerator and the denominator,
    resulting in:

    [ 1 / sin (A)] = csc(A) (Which was to be demonstrated).
  • Nov 25, 2012, 09:03 PM
    JackieF
    Thanks for your help. JackieF

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