Who was The philosopher who is credited with the theorem for the equilateral triangle?

The philosopher credited with the theorem for the equilateral triangle is Euclid, an ancient Greek mathematician. In his work "Elements," he discusses the properties of geometric figures, including equilateral triangles. One of the key results is that the angles in an equilateral triangle are all equal to 60 degrees. Euclid's contributions laid the foundational principles of geometry that are still studied today.