How do you simplify $cos ({tan}^{- 1} (\frac{b}{3}))$ $cos(tan^-1(b/3))$ ?

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Answer 1 · 2016-12-02T16:15:04

$\frac{3}{\sqrt{b^{2} + 9}}$ $3/sqrt(b^2+9)$

Let #a=tan^(-1)(b/3) in [-pi/2, pi/2], wherein cosine is positive.

The given expression is

$cos a = \frac{3}{\sqrt{b^{2} + 9}}$ $cos a = 3/sqrt(b^2+9)$

How do you simplify cos(tan−1(b3))cos(tan^-1(b/3))?