SOLUTION: Evaluate cos[arctan(-5/12)].

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Question 970477: Evaluate cos[arctan(-5/12)].
Answer by lwsshak3(11628) About Me  (Show Source):
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Evaluate cos[arctan(-5/12)]. Interval [0, π]
let x=angle whose tan is (-5/12)
tanx=(-5/12) (working with a (5-12-13) right triangle in quadrant II)
cos[arctan(-5/12)]=cosx=-12/13