Trig

Find the exact trigonometric function of cos(2a).

hyp: 17
opp: 15
adj: 8

asked by Erin
  1. assuming that your given triangle contains angle a
    sina = 15/17, cosa = 8/17
    cos(2a) = cos^2 a - sin^2 a
    = ...

    posted by Reiny

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