`cos(tan^-1 (2))` Find the exact value of the expression. (Hint: Sketch a right triangle.)

Textbook Question

Chapter 4, 4.7 - Problem 55 - Precalculus (3rd Edition, Ron Larson).
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balajia | College Teacher | (Level 1) eNoter

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Taking 2 as oppsite side and 1 as the adjacent side,the hypotenuse will be equal to `sqrt(2^2+1^2)=sqrt(5).`

`tan^-1(2)=cos^-1(1/sqrt(5))`

`cos(tan^-1(2))=cos(cos-1(1/sqrt(5)))=1/sqrt(5).`

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