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-   -   Verifying Trigonometric ldentities (https://www.askmehelpdesk.com/showthread.php?t=185498)

  • Feb 18, 2008, 02:08 PM
    trigsucks09
    Verifying Trigonometric ldentities
    Please help! I've been stuck for hours!
    I need to prove the following identities and I've tried everything and can't get them to work!
    (the * will stand for theta)

    .) sin*+cos*cot*=csc*


    .. ) 1/(1+cos*) + 1/(1-cos*)=2csc2*


    ... ) 1/(sin*) - 1/(tan*)=1


    ... ) sin*/(sin*-cos*)= 1/(1-cot*)


    Please help!
  • Feb 18, 2008, 02:14 PM
    ISneezeFunny
    I usually don't like doing homework on this site for people...

    but I've had a pretty good day so far, so I'll help you out with the first one.

    remember that cot = 1/tan = cos/sin
    remember that csc = 1/sin

    so

    sin* + (cos*)(cos*/sin*) = 1/sin*

    multiply the entire thing by sin*

    sin^2* + cos^2* = sin*/sin*

    sin^2 + cos^2 = 1

    this is true.
  • Feb 19, 2008, 06:05 AM
    revs007
    these all are very simple
    1. let take the left hand side
    sin*+cos* cot*
    sin* + cos* . Cos*/sin*
    taking LCM
    sin^* + cos^* / sin* as sin^*+cos^* = 1
    1/sin*
    cosec* proved


    2. 1/(1+cos*) + 1/(1-cos*)=2csc^*



    again take left hand side to prove
    aftre take lcm it will be

    (1-cos*) + (1+cos*)
    ------------------------
    ( 1-cos*) ( 1+cos*)

    2
    -------------
    (1-cos^*)

    2/sin^*

    2cosec^* proved

    3. 1/(sin*) - 1/(tan*)=1

    seems incomplete question


    4. sin*/(sin*-cos*)= 1/(1-cot*)

    take rhs this time
    1/(1-cot*)


    1
    --- as cot* = cos*/sin*
    1- cos*/sin*


    taking LCm & cross mltipcation

    sin*/sin* -cos* proved

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