anonymous
  • anonymous
Evaluate cos(2Arctan(3/4) ) I know the answer is 7/25 but i'm not sure how to get the answer
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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schrodinger
  • schrodinger
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phi
  • phi
this can be confusing but we we start with tan A = 3/4 and take the arc tangent of both sides (this "undoes" the tangent), we get A = arctan(3/4) so we see that A = arctan(3/4) corresponds to tan A = 3/4 next, we see we want to find cos (2 * arctan(3/4) ) using A = arctan(3/4), this is asking for cos (2A)
phi
  • phi
How do we find the cosine of 2A ? This will take multiple steps We start with A = arctan(3/4) and as noted above, this means tan A = 3/4 draw a triangle: |dw:1378055188769:dw|
anonymous
  • anonymous
do we then use the double angle formula ??

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phi
  • phi
yes, we need cos(2A) = cos^2(A) - sin^2(A)
anonymous
  • anonymous
okay i got it from here Thank You :)

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