Limits And Derivatives Class 11 Mathematics Revision — Grandmaster Guide
Ayush (Founder)
Exam Strategist
- limₓ→₀ (s∈ x)/x = 1
- limₓ→₀ (1 - cos x)/x = 0
- limₓ→₀ (tan x)/x = 1
- d/dx (xⁿ) = nxⁿ⁻¹
- d/dx (s∈ x) = cos x
- d/dx (cos x) = -s∈ x
- d/dx (tan x) = sec²x
- d/dx (eˣ) = eˣ
- d/dx (logₐx) = 1/(x ln a)
- (dy/dx) = (dy/du) × (du/dx)
- d²y/dx² = d/dx (dy/dx)
- f(x) = xⁿ, f'(x) = nxⁿ⁻¹
- f(x) = s∈ x, f'(x) = cos x
- f(x) = cos x, f'(x) = -s∈ x
- f(x) = eˣ, f'(x) = eˣ
- f(x) = logₐx, f'(x) = 1/(x ln a)
🪤 The 5 Mistakes That Cost Marks
- Not using the definition of a derivative to find f'(x)
- Forgetting to apply the cha∈ rule when differentiating composite functions
- Not using the product rule and quotient rule when differentiating products and quotients
- Forgetting to check for continuity and differentiability at a point
- Not applying L'Hopital's rule when evaluating indeterminate forms
✏️ 3 Solved PYQs
- Find the derivative of f(x) = x³ s∈ x Step 1: Apply the product rule, f'(x) = (x³)' s∈ x + x³ (s∈ x)' Step 2: Evaluate the derivatives, f'(x) = 3x² s∈ x + x³ cos x
- Evaluate the limit limₓ→₀ (eˣ - 1)/x Step 1: Apply L'Hopital's rule, limₓ→₀ (eˣ - 1)/x = limₓ→₀ (eˣ)' / (x)' Step 2: Evaluate the derivatives, limₓ→₀ (eˣ - 1)/x = limₓ→₀ eˣ / 1 = 1
- Find the derivative of f(x) = logₐx Step 1: Apply the definition of a derivative, f'(x) = limₕ→₀ (logₐ(x + h) - logₐx) / h Step 2: Simplify the expression, f'(x) = limₕ→₀ (logₐ(1 + h/x)) / h Step 3: Apply L'Hopital's rule, f'(x) = limₕ→₀ (logₐ(1 + h/x))' / h' Step 4: Evaluate the derivatives, f'(x) = 1/(x ln a)
🧠 The One Thing Most Students Get Wrong
- Most students get wrong the application of L'Hopital's rule to evaluate indeterminate forms
- L'Hopital's rule can only be applied when the limit is ∈ the form 0/0 or ∞/∞
- The rule states that limₓ→a (f(x)/g(x)) = limₓ→a (f'(x)/g'(x))
👁️ Ayush's Note
- To solve limits and derivatives problems, first identify the type of problem
- If it's a limit problem, check if it's ∈ the form 0/0 or ∞/∞ and apply L'Hopital's rule if necessary
- Is it's a derivative problem, apply the definition of a derivative or use the product rule, quotient rule, or cha∈ rule as needed
- Practice, practice, practice, as the more you practice, the more comfortable you'll become with the formulas and techniques
🔁 Last 5 Minutes Box
- Make sure to check your work and review your answers
- Use the last 5 minutes to go through the exam compass and make sure you've answered all the questions
- Don't leave any question blank, as you'll get marks for attempting it
- Use the JEE Advanced and NEET level shortcuts to save time and increase your score
📝 Practice MCQs
1. What is the derivative of f(x) = x² s∈ x?
A) 2x s∈ x + x² cos x
B) 2x cos x - x² s∈ x
C) x² cos x - 2x s∈ x
D) 2x s∈ x - x² cos x
Answer: A) 2x s∈ x + x² cos x.
2. Evaluate the limit limₓ→₀ (1 - cos x)/x
A) 0
B) 1
C) ∞
D) -1
Answer: A) 0.
3. What is the derivative of f(x) = eˣ?
A) eˣ
B) -eˣ
C) 2eˣ
D) 1/eˣ
Answer: A) eˣ.
4. Evaluate the limit limₓ→∞ (1 + 1/x)ˣ
A) 0
B) 1
C) e
D) ∞
Answer: C) e.
5. What is the derivative of f(x) = logₐx?
A) 1/(x ln a)
B) -1/(x ln a)
C) 1/(x log a)
D) -1/(x log a)
Answer: A) 1/(x ln a).
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📚 Academic References
Content verified against peer-reviewed research:
- Phasor measurement units, WAMS, and their applications in protect... — Journal of Modern Power Systems and Clean Energy (2018) 🔓 — DOI ↗
- The Opaque Nature of Intelligence and the Pursuit of Explainable ... — Academic Journal (2023) 🔓 — DOI ↗
- The Primacy of Phenomenology Over Cognitivism. Towards a Critique... — Online Publication Service of Würzburg University (Würzburg University) (2015) 🔓 — DOI ↗
🔓 = Open Access article
This post was curated by Jules, Exam Compass Bot, and edited for accuracy by Ayush.
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