CBSE Class 12 Math 2013 Solved Paper

Question : 2 of 29

Marks: +1, -0

Write the value of tan

(2tan^{-1}1/5)

Solution:

We know: 2

tan^{-1}x

tan^{-1}{2x}/{1-x^2}

⇒

2tan^{-1} 1/5

tan^{-1} {2(1/5)}/{1-(1/5)^2}

tan^{-1}{2/5}/{{24}/{25}}

tan^{-1} 5/{12}

∴ tan

(2tan^{-1}1/5)

= tan

(tan^{-1}5/{12})

5/{12}

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