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Provide Solution For R.D.Sharma Maths Class 12 Chapter 10 Differentiation Exercise 10.3 Question 43 Maths Textbook Solution.

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Answer: Hence Prove ,1+a^{2}=b

Hint:

\begin{aligned} &\frac{d}{d x}\left(x^{n}\right)=n x^{n-1} \\ &\frac{d(\text { constant) }}{d x}=0 \end{aligned}

Given:

\frac{d}{\mathrm{dx}}\left[\tan ^{-1}(\mathrm{a}+\mathrm{bx})\right]=1 \text { at } \mathrm{x}=0

Solution:

So, using chain rule,

we know \frac{d}{d x}\left(\tan ^{-1} x\right)=\frac{1}{1+x^{2}}

\begin{aligned} &{\left[\left\{\frac{1}{1+(a+b x)^{2}}\right\} \frac{d}{dx}(a+b x)\right]_{x=0}=1} \\ &{\left[\frac{1}{1+(a+b x)^{2}} \times(b)\right]_{x=0}=1} \\ &{\left[\frac{b}{\left[1+(a+b x)^{2}\right.}\right]_{x=0}=1} \\ &\therefore(a+b)^{2}=a^{2}+b^{2}+2 a b \end{aligned}

\begin{aligned} &{\left[\frac{b}{1+\left(a^{2}+b^{2} x^{2}+2 a b x\right)}\right]_{x=0}=1} \\ &\frac{b}{1+\left(a^{2}+0+0\right)}=1 \\ &\frac{b}{1+a^{2}}=1 \\ &b=1+a^{2} \end{aligned}

Hence Proved,

 

    

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