Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 11

# If Tan α = 1 1 + 2 − X and Tan β = 1 1 + 2 X + 1 Then Write the Value of α + β Lying in the Interval ( 0 , π 2 ) - Mathematics

Short Note

If tan $\alpha = \frac{1}{1 + 2^{- x}}$ and $\tan \beta = \frac{1}{1 + 2^{x + 1}}$ then write the value of α + β lying in the interval $\left( 0, \frac{\pi}{2} \right)$

#### Solution

$\tan(\alpha + \beta) = \frac{\tan\alpha + \tan\beta}{1 - \tan\alpha\tan\beta}$

$= \frac{\frac{1}{1 + 2^{- x}} + \frac{1}{1 + 2^{x + 1}}}{1 - \frac{1}{(1 + 2^{- x} )(1 + 2^{x + 1} )}}$

$= \frac{1 + 2^{x + 1} + 1 + 2^{- x}}{1 + 2^{x + 1} + 2^{- x} + 2^{- x + x + 1} - 1}$

$= \frac{2 + 2^{x + 1} + 2^{- x}}{2 + 2^{x + 1} + 2^{- x}}$

$= 1$

$\text{ Therefore }, \alpha + \beta = \tan^{- 1} (1) = \frac{\pi}{4} .$

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#### APPEARS IN

RD Sharma Class 11 Mathematics Textbook
Chapter 7 Values of Trigonometric function at sum or difference of angles
Q 12 | Page 27