MCQ
If $f(x) = x\, {\tan ^{ - 1}}x$, then $f'(1) =$
- A$1 + {\pi \over 4}$
- ✓${1 \over 2} + {\pi \over 4}$
- C${1 \over 2} - {\pi \over 4}$
- D$2$
Differentiating w.r.t $ x,$ we get $f'(x) = x\frac{1}{{1 + {x^2}}} +{\tan ^{ - 1}}x$
Now put $x = 1$, then $f'(1) = \frac{1}{2} + {\tan ^{ - 1}}(1) = \frac{\pi }{4} + \frac{1}{2}$.
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$\text{a}=1,\text{ b}=-1$
$\text{a}=-1,\text{ b}=1+\sqrt{2}$
$\text{a}=-1,\text{ b}=1$
$\text{None os these}.$