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In calculus, the **general Leibniz rule**,^{[1]} named after Gottfried Wilhelm Leibniz, generalizes the product rule (which is also known as "Leibniz's rule"). It states that if and are n-times differentiable functions, then the product is also n-times differentiable and its n-th derivative is given by

where is the binomial coefficient and denotes the

The rule can be proven by using the product rule and mathematical induction.

If, for example, *n* = 2, the rule gives an expression for the second derivative of a product of two functions:

The formula can be generalized to the product of *m* differentiable functions *f*_{1},...,*f*_{m}.

The proof of the general Leibniz rule proceeds by induction. Let and be -times differentiable functions. The base case when claims that:

Then,

With the multi-index notation for partial derivatives of functions of several variables, the Leibniz rule states more generally:

This formula can be used to derive a formula that computes the symbol of the composition of differential operators. In fact, let *P* and *Q* be differential operators (with coefficients that are differentiable sufficiently many times) and Since *R* is also a differential operator, the symbol of *R* is given by:

A direct computation now gives:

This formula is usually known as the Leibniz formula. It is used to define the composition in the space of symbols, thereby inducing the ring structure.

- Binomial theorem – Algebraic expansion of powers of a binomial
- Derivation (differential algebra) – Algebraic generalization of the derivative
- Derivative – Instantaneous rate of change (mathematics)
- Differential algebra – Algebraic study of differential equations
- Pascal's triangle – Triangular array of the binomial coefficients in mathematics
- Product rule – Formula for the derivative of a product
- Quotient rule – Formula for the derivative of a ratio of functions