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Math Help - Help verifying trig identities

  1. #1
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    Help verifying trig identities

    I'm having a little bit of trouble verifying 2 trig identities. One of these may not even be an identity but I don't know which one since I'm having trouble with both.
    The first one is:

    sin(x+y)/sin(x-y) = 1-tanxtany/1+tanxtany

    And the second one is:

    (sinx/1-cotx) - (cosx/tanx-1) = sinx+cosx

    I get to a certain point on both of these and can't figure out where to go from there, any help in how to verify these would be GREATLY appreciated!!

    Thanks!
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  2. #2
    Senior Member abhishekkgp's Avatar
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    Quote Originally Posted by sam1219 View Post
    I'm having a little bit of trouble verifying 2 trig identities. One of these may not even be an identity but I don't know which one since I'm having trouble with both.
    The first one is:

    sin(x+y)/sin(x-y) = 1-tanxtany/1+tanxtany

    This is wrong. you should take reciprocal of the RHS to fix this one

    And the second one is:

    (sinx/1-cotx) - (cosx/tanx-1) = sinx+cosx
    please bracket it properly so that i can give you a definitive answer.

    I get to a certain point on both of these and can't figure out where to go from there, any help in how to verify these would be GREATLY appreciated!!

    Thanks!
    did this help?
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  3. #3
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    So are you saying the first one is not an identity? That is the problem that was given to me and I'm asked to verify it, so by wrong do you mean it's not an identity?

    and I'm not sure how you want me to bracket the second one properly, but here's another try at what it looks like

    Sinx - cosx = sinx + cosx
    1-cotx tanx-1
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  4. #4
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    Hello, sam1219!



    This one is not an identity . . .






    . .


    . .








    . .


    . .

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  5. #5
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    Thank you so much! You are awesome!!
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