Quotient And Product Rule: Formula & Examples

Quotient And Product Rule: Formula & Examples

Quotient And Product Rule: Quotient rule is a formal rule for differentiating problems where one function is divided by another. It follows from the limit definition of derivative and is given by. Remember the rule in the following way. Always start with the “bottom” function and end with the “bottom” function squared. The quotient rule is defined as the quantity of the denominator times the derivative of the numerator minus the numerator times the derivative of the denominator all over the denominator squared.

The Product Rule says that the derivative of a product of two functions is the first function times the derivative of the second function plus the second function times the derivative of the first function. The Product Rule must be utilized when the derivative of the quotient of two functions is to be taken.

Quotient Rule Derivative

Definition and Formula

The quotient rule is a formula for taking the derivative of a quotient of two functions. It makes it somewhat easier to keep track of all of the terms. Let’s look at the formula.

If you have function f(x) in the numerator and the function g(x) in the denominator, then the derivative is found using this formula:

Quotient Rule Derivative formula

Quotient Rule Derivative formula

Take g(x) times the derivative of f(x).In this formula, the d denotes a derivative. So, df(x) means the derivative of function f and dg(x) means the derivative of function g. The formula states that to find the derivative of f(x) divided by g(x), you must:

  1. Then from that product, you must subtract the product of f(x) times the derivative of g(x).
  2. Finally, you divide those terms by g(x) squared.

Mnemonic Device

The quotient rule formula may be a little difficult to remember. Perhaps a little yodeling-type chant can help you. Imagine a frog yodeling, ‘LO dHI less HI dLO over LO LO.’ In this mnemonic device, LO refers to the denominator function and HI refers to the numerator function.

Quotient Rule Derivative

Quotient Rule Derivative

Let’s translate the frog’s yodel back into the formula for the quotient rule.

LO dHI means denominator times the derivative of the numerator: g(x) times df(x).

less means ‘minus’.

HI dLO means numerator times the derivative of the denominator: f(x) times dg(x).

over means ‘divide by’.

LO LO means to take the denominator times itself: g(x) squared.

Quotient Rule Derivative Formula

Now, we want to be able to take the derivative of a fraction like f/g, where f and g are two functions. This one is a little trickier to remember, but luckily it comes with its own song. The formula is as follows:

formula

formula

How to Remember this Formula (with thanks to Snow White and the Seven Dwarves):

Replacing f by hi and g by ho (hi for high up there in the numerator and ho for low down there in the denominator), and letting D stand-in for `the derivative of’, the formula becomes:

how to remember formula

how to remember formula

In words, that is “ho dee hi minus hi dee ho over ho ho”. Now, if Sleepy and Sneezy can remember that, it shouldn’t be any problem for you.

As an example,

example

example

A Common Mistake: Remembering the quotient rule wrong and getting an extra minus sign in the answer. It’s very easy to forget whether it’s ho dee hi first (yes, it is) or hi dee ho first (no, it’s not).

Derivative Product And Quotient Rule

If e(x) = f(x) . g(x) and if both derivatives exist, then
e ‘(x) = f(x) . g'(x) + f(x) . g'(x)
In words, this means the derivative of a product is the first function times the derivative of the second function plus the second function times the derivative of the first function.

product rule

product rule

Partial Derivative Quotient Rule

Partial derivatives in calculus are derivatives of multivariate functions taken with respect to only one variable in the function, treating other variables as though they were constants. Repeated derivatives of a function f(x,y) may be taken with respect to the same variable, yielding derivatives Fxx and Fxxx, or by taking the derivative with respect to a different variable, yielding derivatives Fxy, Fxyx, Fxyy, etc. Partial derivatives are typically independent of the order of differentiation, meaning Fxy = Fyx.

partial derivative

partial derivative

Calculate the derivative of the function f(x,y) with respect to x by determining d/dx (f(x,y)), treating y as if it were a constant. Use the product rule and/or chain rule if necessary. For example, the first partial derivative Fx of the function f(x,y) = 3x^2*y – 2xy is 6xy – 2y.

Calculate the derivative of the function with respect to y by determining d/dy (Fx), treating x as if it were a constant. In the above example, the partial derivative Fxy of 6xy – 2y is equal to 6x – 2.

What is the definition of the quotient rule?

Similar to product rule, the quotient rule is a way of differentiating the quotient, or division of functions. The quotient rule is defined as the quantity of the denominator times the derivative of the numerator minus the numerator times the derivative of the denominator all over the denominator squared.

Why does the quotient rule work?

The quotient rule is a rule used to find the derivative of a function that can be written as the quotient of two functions. More simply, you can think of the rule as applying to functions that are written out as fractions, where the numerator and the denominator are both themselves functions.

What is the Leibniz product rule?

In calculus, the general Leibniz rule, named after Gottfried Wilhelm Leibniz, generalizes the product rule (which is also known as “Leibniz’s rule”). It states that if and are -times differentiable functions, then the product is also -times differentiable and its derivative is given by.

What is the definition of product rule?

The product rule is a formal rule for differentiating problems where one function is multiplied by another. The rule follows from the limit definition of derivative and is given by. Remember the rule in the following way. Each time, differentiate a different function in the product and add the two terms together.

What is the product rule in probability?

The rule of product is a guideline as to when probabilities can be multiplied to produce another meaningful probability. Specifically, the rule of product is used to find the probability of an intersection of events: Let A and B be independent events.

How do you solve product rule?

The product rule is if the two “parts” of the function are being multiplied together, and the chain rule is if they are being composed. For instance, to find the derivative of f(x) = x² sin(x), you use the product rule, and to find the derivative of g(x) = sin(x²) you use the chain rule.

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