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Math Help - obtuse basic trig -ve solution

  1. #1
    Member i_zz_y_ill's Avatar
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    obtuse basic trig -ve solution

    a is obtuse such that sina=1/5 find the exact value of cosa

    I did c^2+s^2=1


    and cosa = =+/-(24^0.5)/5

    but the aswer is just the negative root,,,is this always the case when obtuse simply or is this answer wrong?
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    Quote Originally Posted by i_zz_y_ill View Post
    a is obtuse such that sina=1/5 find the exact value of cosa I did c^2+s^2=1 and cosa = =+/-(24^0.5)/5
    but the aswer is just the negative root,,,is this always the case when obtuse simply or is this answer wrong?
    Cosine is negative in II. We are given that a is obtuse.
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