Using the distance formula, you can determine the lengths of the sides of the shape. This will help determine if triangles are equilateral, isosceles or scalene; or if quadrilaterals are squares, rectangles, rhombi, or isosceles trapezoids; or if other polygons are regular polygons. The slope formula will tell help you determine if two sides are parallel. In a quadrilateral, this will help you determine if the figure is a parallelogram or a trapezoid.