You memorized the power rule. Now your professor throws x²·sin(x) at you and expects you to know what to do. That's where the product rule, quotient rule, and chain rule come in.
This guide covers every differentiation rule you need — with examples that actually make sense.
The Four Core Rules
1. Power Rule — The Foundation
d/dx(xⁿ) = n · xⁿ⁻¹
This handles polynomials. For f(x) = 3x⁴ − 2x² + 7:
f'(x) = 12x³ − 4x
Constants vanish. Exponents come down. Done.
2. Product Rule — Two Functions Multiplied
When f(x) = u(x) · v(x):
(uv)' = u'v + uv'
Translation: derivative of first × second + first × derivative of second.
Example: f(x) = x² · eˣ
- u = x², u' = 2x
- v = eˣ, v' = eˣ
- f'(x) = 2x·eˣ + x²·eˣ = eˣ(2x + x²)
3. Quotient Rule — One Function Divided by Another
When f(x) = u(x) / v(x):
(u/v)' = (u'v − uv') / v²
Example: f(x) = (3x + 1) / (x − 2)
- u = 3x + 1, u' = 3
- v = x − 2, v' = 1
- f'(x) = [3(x−2) − (3x+1)(1)] / (x−2)²
- f'(x) = (3x − 6 − 3x − 1) / (x−2)²
- f'(x) = −7 / (x−2)²
4. Chain Rule — Functions Inside Functions
When f(x) = g(h(x)):
f'(x) = g'(h(x)) · h'(x)
Example: f(x) = sin(3x²)
- Outer: sin(u) → cos(u)
- Inner: 3x² → 6x
- f'(x) = cos(3x²) · 6x = 6x·cos(3x²)
Which Rule Do I Use? Decision Tree
| Situation | Rule | Example | |-----------|------|---------| | Single polynomial term | Power Rule | x⁵ → 5x⁴ | | Two functions multiplied | Product Rule | x²·sin(x) | | One function divided by another | Quotient Rule | (x+1)/(x−1) | | Function inside a function | Chain Rule | e^(2x) → 2e^(2x) | | Multiple rules needed | Combine them | x²·sin(3x) |
The Trench Truth: The #1 mistake on derivative exams is using the product rule when the power rule alone suffices. For 3x⁴, just use the power rule — don't split it into 3 · x⁴ and apply the product rule. You'll get the same answer but waste time and invite arithmetic errors.
Common Derivatives Reference Table
| Function | Derivative | Function | Derivative | |----------|-----------|----------|-----------| | xⁿ | nxⁿ⁻¹ | eˣ | eˣ | | sin(x) | cos(x) | cos(x) | −sin(x) | | tan(x) | sec²(x) | ln(x) | 1/x | | logₐ(x) | 1/(x·ln a) | aˣ | aˣ·ln a |
Real-World Applications
- Physics: Velocity is the derivative of position. Acceleration is the derivative of velocity.
- Economics: Marginal cost = derivative of total cost. Marginal revenue = derivative of total revenue.
- Biology: Population growth rate = derivative of population over time.
Try our derivative calculator to verify your work on any polynomial.
Related: Integral Calculator · Quadratic Formula Calculator · Square Root Calculator
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