Triangle Side Length Calculator using Law of Cosines

The calculator uses the law of cosines, which is a generalization of the Pythagorean theorem, to compute the length of the third side of a triangle given the lengths of two sides and the angle between them. The law of cosines states that the square of the length of the third side (C) is equal to the sum of the squares of the lengths of the other two sides (A and B) minus twice the product of the lengths of those sides and the cosine of the angle between them (θ). Mathematically, it can be represented as

To use the calculator, the user needs to enter the lengths of the two known sides (A and B) and the angle between them (θ) in degrees. The calculator will then apply the law of cosines to compute the length of the unknown side (C) and display the result. This tool can be particularly useful in geometry and trigonometry problems involving triangles, where the length of one side is unknown but the lengths of the other two sides and the angle between them are known.

Side length of a triangle

Side A

Side B

Angle (degrees)

Calculation precision

Digits after the decimal point: 2

Calculate

Side C

 

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