# Trigonometric Ratio: Cotangent

How to solve cotangent (trigonometric ratio) problems: definition, example, and its solution.

## Definition

Cotangent is the reciprocal of tangent.

Tangent: TOA.

[tan *A* = (**O**pposite side) / (**A**djacent)]

So cot *A* = (**A**djacent) / (**O**pposite side).

## Example

cot *A* = (adjacent side) / (opposite side)

In the given right triangle,

the adjacent side is missing.

So find the adjacent side

by using the Pythagorean theorem.

(adjacent side) = √21

cot *A* = 1 / tan *A*

Tangent: TOA.

So tan *A* = 2/√21.

So, its reciprocal, cotangent is

cot *A* = √21/2.