# Derivative of Cos Inverse – Formula, Definition, Examples

Created on Jan 15, 2024

Updated on January 15, 2024

Understanding the derivative of the cos inverse or arccos is a crucial part of learning calculus, particularly for students embarking on a math course. This fundamental concept is not just theoretical but also finds practical applications in various fields. In this expanded introduction, we will delve into the derivative of cos inverse (arccos), its formula, and its importance in calculus, making it accessible for math for kids and guided by a math tutor for kids.

## What is the Derivative of Cos Inverse (Arccos) ?

The cos inverse function, denoted as arccos(x) or cos⁻¹(x), is essential in understanding trigonometric functions. Its derivative, d/dx [arccos(x)], is a cornerstone in calculus, particularly when dealing with integrals and differential equations. This derivative is especially relevant in a math course aimed at children, where concepts are broken down into simpler, more comprehensible parts.

## Concept and Definition of Arccos

Arccos, the angle whose cosine is a given number, is an integral concept in trigonometry. For instance, arccos(0.5) finds the angle with a cosine of 0.5, which is π/3 in radians. Understanding arccos is a stepping stone in a math tutor for kids program, simplifying complex ideas for young learners.

## Derivative of Cos Inverse Formula

The formula for the derivative of cos inverse is given by:

$(d/dx) [arccos(x)]=−1/(√1-x²) $

This formula indicates that the derivative of arccos(x) is the negative reciprocal of the square root of 1 minus x squared. The formula is derived using the chain rule and trigonometric identities, which we will explore in the next section.

## Deriving the Derivative of Cos Inverse By First Principles

The derivative of cos inverse can be derived from first principles using the limit definition of a derivative and trigonometric identities. Here’s a simple step-by-step explanation:

- Start with the definition of the derivative: $f_{′}(x)=(ℎ→0)((f(x+h)−f(x))/h) $
- Apply this definition to arccos(x).
- Use trigonometric identities to simplify the expression.
- Take the limit as h approaches 0.

This process leads to the aforementioned formula for the derivative of cos inverse.

## Relationship Between Derivative of Cos Inverse and Sin Inverse

The derivatives of cos inverse and sin inverse are closely related. The derivative of sin inverse is 1/(√1-x²), which is similar but not negative like the derivative of cos inverse. This relationship helps in understanding the symmetry and properties of trigonometric functions.