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Math Help - Really basic trig question

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    Really basic trig question

    OK:
    arsin(sin(5p\7)) = 2p/7
    arctan(tan(5p/5))= -p/5

    Why is the second answer negative?
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    Re: Really basic trig question

    Quote Originally Posted by Nervous View Post
    OK:
    arsin(sin(5p\7)) = 2p/7
    arctan(tan(5p/5))= -p/5

    Why is the second answer negative?
    The angle must be in the second quadrant...
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    Re: Really basic trig question

    Quote Originally Posted by Nervous View Post
    OK:
    arsin(sin(5p\7)) = 2p/7
    arctan(tan(5p/5))= -p/5

    Why is the second answer negative?
    uhhh ... arctan((tan(5pi/5)) = \arctan(tan(pi)) = \arctan(0) = 0
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    Re: Really basic trig question

    Quote Originally Posted by skeeter View Post
    uhhh ... arctan((tan(5pi/5)) = \arctan(tan(pi)) = \arctan(0) = 0
    I must have misunderstood the question, I thought that p was representing some unknown, not \displaystyle \begin{align*} \pi \end{align*} ...
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    Re: Really basic trig question

    Quote Originally Posted by Prove It View Post
    I must have misunderstood the question, I thought that p was representing some unknown, not \displaystyle \begin{align*} \pi \end{align*} ...
    first solution is ...
    arsin(sin(5p\7)) = 2p/7
    what else could "p" be?
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