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Math Help - Arctan and getting a value outside the defined set

  1. #1
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    Arctan and getting a value outside the defined set

    I want to solve:
    2arctan(2)+arcsin(4/5).
    I am doing this by setting
    arctan(tan(2arctan(2)+arcsin(4/5))
    and then by using the addition formula for tangens twice I get arctan(0)=0
    But here is the thing, my text book want's it to be pi.
    I can't see how it can since the arctan can never be anything outside [-pi/2,pi/2] right?
    So what do I do wrong, anyone?
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  2. #2
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    Quote Originally Posted by a4swe View Post
    I want to solve:
    2arctan(2)+arcsin(4/5).
    I am doing this by setting
    arctan(tan(2arctan(2)+arcsin(4/5))
    and then by using the addition formula for tangens twice I get arctan(0)=0
    But here is the thing, my text book want's it to be pi.
    I can't see how it can since the arctan can never be anything outside [-pi/2,pi/2] right?
    So what do I do wrong, anyone?
    Where is the equation?
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  3. #3
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    There is no equation afaik.
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