Class CBSE Class 12 Mathematics Derivatives Q #1439
COMPETENCY BASED
REMEMBER
5 Marks 2025 AISSCE(Board Exam) LA
For a positive constant 'a', differentiate $a^{t+\frac{1}{t}}$ with respect to $(t+\frac{1}{t})^{a}$ where t is a non-zero real number.

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Detailed Solution

Step 1: Define the functions

Let $u = a^{t+\frac{1}{t}}$ and $v = (t+\frac{1}{t})^a$. We need to find $\frac{du}{dv}$.

Step 2: Differentiate u with respect to t

We have $u = a^{t+\frac{1}{t}}$. Taking the natural logarithm of both sides, we get $\ln u = (t+\frac{1}{t}) \ln a$. Differentiating both sides with respect to $t$, we have $$ \frac{1}{u} \frac{du}{dt} = \ln a \cdot (1 - \frac{1}{t^2}) $$ $$ \frac{du}{dt} = u \ln a \cdot (1 - \frac{1}{t^2}) = a^{t+\frac{1}{t}} \ln a \cdot (1 - \frac{1}{t^2}) $$

Step 3: Differentiate v with respect to t

We have $v = (t+\frac{1}{t})^a$. Taking the natural logarithm of both sides, we get $\ln v = a \ln (t+\frac{1}{t})$. Differentiating both sides with respect to $t$, we have $$ \frac{1}{v} \frac{dv}{dt} = a \cdot \frac{1}{t+\frac{1}{t}} \cdot (1 - \frac{1}{t^2}) $$ $$ \frac{dv}{dt} = v \cdot a \cdot \frac{1}{t+\frac{1}{t}} \cdot (1 - \frac{1}{t^2}) = (t+\frac{1}{t})^a \cdot a \cdot \frac{1}{t+\frac{1}{t}} \cdot (1 - \frac{1}{t^2}) = a (t+\frac{1}{t})^{a-1} (1 - \frac{1}{t^2}) $$

Step 4: Find du/dv

We need to find $\frac{du}{dv} = \frac{du/dt}{dv/dt}$. $$ \frac{du}{dv} = \frac{a^{t+\frac{1}{t}} \ln a \cdot (1 - \frac{1}{t^2})}{a (t+\frac{1}{t})^{a-1} (1 - \frac{1}{t^2})} = \frac{a^{t+\frac{1}{t}} \ln a}{a (t+\frac{1}{t})^{a-1}} $$ $$ \frac{du}{dv} = \frac{a^{t+\frac{1}{t}-1} \ln a}{(t+\frac{1}{t})^{a-1}} $$

Final Answer: $\frac{a^{t+\frac{1}{t}-1} \ln a}{(t+\frac{1}{t})^{a-1}}$

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Pedagogical Audit
Bloom's Analysis: This is an REMEMBER question because the student needs to recall the differentiation rules and apply them to solve the problem.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the student to apply differentiation rules and logarithmic properties, which falls under procedural knowledge.
Syllabus Audit: In the context of CBSE Class 12, this is classified as Application of Derivatives. The question involves differentiating composite functions and applying the chain rule, which are standard topics in this chapter.