Trigonometric Ratio: Cotangent

Trigonometric Ratio: Cotangent

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

Definition

cot A = 1/tan A = (Adjacent side) / (Opposite side)

Cotangent is the reciprocal of tangent.

Tangent: TOA.
[tan A = (Opposite side) / (Adjacent)]

So cot A = (Adjacent) / (Opposite side).

Example

Find cot A. For a right triangle: Hypotenuse: 5, Opposite side: 2

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.