Continuity and Differentiability
Punjab Board · Class 12 · Mathematics
Complete topic list for Continuity and Differentiability in Punjab Board Class 12 Mathematics. Key concepts, sub-topics, and what to focus on for board exams.
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Explore the full setTopics in Continuity and Differentiability
1. Continuity of a Function
- A function f(x) is continuous at x = c if: lim(x→c) f(x) = f(c). This single condition contains three sub-conditions: (a) f(c) must exist, (b) lim(x→c) f(x) must exist, and (c) both must be equal.
- For the limit to exist, the Left Hand Limit (LHL) must equal the Right Hand Limit (RHL): lim(x→c⁻) f(x) = lim(x→c⁺) f(x).
- A function is continuous on an interval if it is continuous at every point in that interval.
2. Algebra of Continuous Functions
- If f and g are both continuous at x = c, then: f+g, f-g, f·g are all continuous at x = c.
- f/g is continuous at x = c provided g(c) ≠ 0.
- A constant multiple λ·f is continuous wherever f is continuous.
3. Differentiability
- The derivative of f at c is: f'(c) = lim(h→0) [f(c+h) - f(c)] / h, provided this limit exists.
- f is differentiable at c if both the Left Hand Derivative (LHD) and Right Hand Derivative (RHD) exist and are equal.
- LHD at c = lim(h→0⁻) [f(c+h) - f(c)] / h
4. Chain Rule and Derivatives of Composite Functions
- Chain Rule: If y = f(u) and u = g(x), then dy/dx = (dy/du) · (du/dx).
- In words: differentiate the outer function keeping inner function unchanged, then multiply by derivative of inner function.
- For three levels: if y = f(v), v = g(u), u = h(x), then dy/dx = (dy/dv)·(dv/du)·(du/dx).
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