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The SSS congruence test

The initials SSS stand for 'Side', 'Side', 'Side'.

You need to be given three side lengths of a triangle (two is not enough) to be able to construct a triangle that is unique up to congruence.

A three-sided triangle is constructed in the following stages.

3 circles of different sizes
Detailed description

This method can be used for constructing any triangle where three lengths have been given. (The sum of the two shortest lengths must be greater than the third length for the triangle to exist.)