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Provide Solution for RD Sharma Class 12 Chapter 10 Differentiation Exercise 10.7 Question 20

Answers (1)

Answer:

            \frac{d y}{d x}=\frac{(a)^{t+\frac{1}{t}} \cdot \log a}{a\left(t+\frac{1}{t}\right)^{a-1}}

Hint:

            Use chain rule and   \frac{d y}{d x}=\frac{\frac{d y}{d t}}{\frac{d x}{d t}}

Given:

            \begin{aligned} &x=\left(t+\frac{1}{t}\right)^{a} \\ &y=(a)^{t+\frac{1}{t}} \end{aligned}

Solution:

x=\left(t+\frac{1}{t}\right)^{a} \\

\begin{aligned} & &\frac{d x}{d t}=\frac{d\left(t+\frac{1}{t}\right)}{d t} \end{aligned}

=\frac{d\left(t+\frac{1}{t}\right)^{a}}{d\left(t+\frac{1}{t}\right)} \times \frac{d\left(t+\frac{1}{t}\right)}{d t}                      [Using chain rule]

=a\left(t+\frac{1}{t}\right)^{a-1} \times\left(\frac{d t}{d t}+\frac{d\left(\frac{1}{t}\right)}{d t}\right)                  \left[\because \frac{d x^{n}}{d x}=n x^{n-1}\right]

=a\left(t+\frac{1}{t}\right)^{a-1} \times\left(1+\left(\frac{-1}{t^{2}}\right)\right) \\

\begin{aligned} & &\frac{d x}{d t}=a\left(t+\frac{1}{t}\right)^{a-1} \times\left(1-\frac{1}{t^{2}}\right) \end{aligned}                                                                                                       (1)

y=a^{t+\frac{1}{t}} \\

\frac{d y}{d x}=\frac{d\left(a^{1+\frac{1}{t}}\right)}{d t} \\

\begin{aligned} & &=\frac{d\left(a^{t+\frac{1}{t}}\right)}{d\left(t+\frac{1}{t}\right)} \times \frac{d\left(t+\frac{1}{t}\right)}{d t} \end{aligned}

=\left(a^{t+\frac{1}{t}}\right) \log a \times\left(\frac{d t}{d t}+\frac{d\left(\frac{1}{t}\right)}{d t}\right)                          \quad\left[\because \frac{d\left(a^{x}\right)}{d x}=a^{x} \log a\right]

\frac{d y}{d t}=(a)^{t+\frac{1}{t}} \log a \times\left[1-\frac{1}{t^{2}}\right]                                                                                                                                        (2)

\begin{aligned} & \\ &\frac{d y}{d x}=\frac{\frac{d y}{d t}}{\frac{d x}{d t}} \end{aligned}

Put the values of  \frac{d x}{d t} \text { and } \frac{d y}{d t}  from equation (1) and (2) respectively

\frac{d y}{d x}=\frac{(a)^{r+\frac{1}{1}} \times \log a \times\left(1-\frac{1}{t^{2}}\right)}{a\left(t+\frac{1}{t}\right)^{a-1} \times\left(1-\frac{1}{t^{2}}\right)} \\

\begin{aligned} & &\frac{d y}{d x}=\frac{(a)^{t+\frac{1}{t}} \log a}{a\left(t+\frac{1}{t}\right)^{a-1}} \end{aligned}

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