## formal version of def. of derivative

### The derivative of a function is a fundamental concept in calculus that measures the rate at which a function changes at a specific point

The derivative of a function is a fundamental concept in calculus that measures the rate at which a function changes at a specific point. It provides crucial information about the behavior of a function and has applications in various fields such as physics, engineering, and economics.

Formally, let f(x) be a function defined on an interval containing the point x = a. The derivative of f at x = a, denoted as f'(a) or dy/dx∣x=a, is defined as the limit of the difference quotient as h approaches 0:

f'(a) = lim(h→0) [f(a + h) – f(a)]/h

Geometrically, the derivative represents the slope or steepness of the tangent line to the graph of the function at the point (a, f(a)). If the derivative is positive, the function is increasing at that point, while a negative derivative indicates the function is decreasing. A derivative of zero suggests a horizontal tangent line and a possible extremum (maximum or minimum) point.

The derivative can be interpreted as the instantaneous rate of change of a function, measuring how much the function output changes for a small change in the input variable. It provides insight into the behavior of functions, including determining critical points, finding extrema, and understanding the concavity of a function.

The derivative can also be expressed using alternative notations, such as Leibniz’s notation: dy/dx, prime notation: f'(x), or Lagrange’s notation: Df(x). These notations represent the same concept of the derivative and are used interchangeably depending on the context.

##### More Answers:

Understanding the Product Rule in Calculus | Finding the Derivative of the Product of Two FunctionsUnderstanding d/dx Notation and Calculating the Derivative of f(g(x))

Understanding Continuity in Mathematics | Definition and Importance