Product Rule and Quotient Rule

TL;DR

The video explains the product and quotient rules for finding derivatives, showing examples and patterns.

Transcript

PROFESSOR: OK. This video is about derivatives. Two rules for finding new derivatives. If we know the derivative of a function f-- say we've found that-- and we know the derivative of g-- we've found that-- then there are functions that we can build out of those. And two important and straightforward ones are the product, f of x times g of x, and t... Read More

Key Insights

• 📏 The product rule and the quotient rule are important rules for finding derivatives of products and quotients of functions.
• ⌛ The product rule states that the derivative of a product is the first function times the derivative of the second plus the second function times the derivative of the first.
• ⌛ The quotient rule states that the derivative of a quotient is the denominator times the derivative of the numerator minus the numerator times the derivative of the denominator, divided by the denominator squared.
• 📏 These rules can be used to find derivatives of functions with both positive and negative exponents.
• ☺️ The pattern for finding the derivative of a power of x is that the exponent comes down and the power of x is decreased by one.
• ☺️ The quotient rule can be used to find the derivative of trigonometric functions, such as sine x over cosine x.

Questions & Answers

Q: What is the product rule for finding derivatives?

The product rule states that the derivative of a product of two functions is the first function times the derivative of the second plus the second function times the derivative of the first. It can be represented as (f(x)g'(x)) + (g(x)f'(x)).

Q: How do you apply the product rule to find the derivative of a cubic function?

To find the derivative of a cubic function using the product rule, you multiply the first function (x^3) by the derivative of the second function (which is 1) and add it to the second function (x) multiplied by the derivative of the first function (which is 2x). Simplifying the expression gives you the derivative as 3x^2.

Q: What is the quotient rule for finding derivatives?

The quotient rule states that the derivative of a quotient of two functions is the denominator times the derivative of the numerator minus the numerator times the derivative of the denominator, divided by the denominator squared. It can be represented as (g(x)f'(x) - f(x)g'(x)) / g(x)^2.

Q: How do you apply the quotient rule to find the derivative of a function with a negative power?

To find the derivative of a function with a negative power using the quotient rule, you first rewrite the function as an exponentiation with a positive power. Then, you can apply the quotient rule as usual. The derivative will be -(n * x^(-n-1)), where n is the exponent.

Summary & Key Takeaways

• The video explains the two important rules for finding derivatives: the product rule and the quotient rule.

• The product rule states that the derivative of a product of two functions is the first function times the derivative of the second plus the second function times the derivative of the first.

• The quotient rule states that the derivative of a quotient of two functions is the denominator times the derivative of the numerator minus the numerator times the derivative of the denominator, divided by the denominator squared.