Class CBSE Class 12 Mathematics Continuity and Differentiability Q #1692
COMPETENCY BASED
EVALUATE
1 Marks 2026 AISSCE(Board Exam) MCQ SINGLE
The value of k for which the function $f(x)=\begin{cases} x^{2}\sin\frac{1}{x}, & x\ne0 \\ k(x+1), & x=0 \end{cases}$ is a continuous function, is:
(A) $\frac{1}{4}$
(B) 2
(C) $\frac{1}{2}$
(D) 0
Correct Answer: D

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Detailed Solution

Step 1: Condition for Continuity

A function $f(x)$ is continuous at $x=0$ if the limit of the function as $x$ approaches $0$ is equal to the value of the function at $x=0$. That is: $$\lim_{x \to 0} f(x) = f(0)$$

Step 2: Evaluate the Limit

We need to find $\lim_{x \to 0} x^{2}\sin(\frac{1}{x})$. Since $-1 \le \sin(\frac{1}{x}) \le 1$, we can use the Squeeze Theorem: $$-x^2 \le x^2\sin\left(\frac{1}{x}\right) \le x^2$$ As $x \to 0$, both $-x^2$ and $x^2$ approach $0$. Therefore, by the Squeeze Theorem, the limit is $0$.

Step 3: Evaluate f(0)

From the definition of the function, $f(0) = k(0+1) = k$.

Step 4: Equate and Solve

Equating the limit to the function value: $$0 = k$$ Thus, $k = 0$.

Final Answer: 0

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Pedagogical Audit
Bloom's Analysis: This is an EVALUATE question because the student must determine the validity of the continuity condition by applying the Squeeze Theorem to a limit.
Knowledge Dimension: PROCEDURAL
Justification: The student must execute a specific sequence of steps involving limit evaluation and algebraic substitution to find the unknown constant.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. This question tests the conceptual understanding of continuity at a point, a core topic in the Calculus unit of the CBSE Mathematics syllabus.