Triangle: a figure surrounded by three line segments. Area = 1/2 base× height square: perimeter = side length× 4, area = side length× side length rectangle: perimeter = (length+width )× 2, area = length× width parallelogram: two groups of parallelograms with opposite sides are called parallelograms. Area = base × height trapezoid: only a set of quadrangles with parallel opposite sides is called trapezoid. A group of mutually parallel opposite sides in a trapezoid are called the upper and lower bottom sides of the trapezoid, and a group of non-parallel sides are called the waist of the trapezoid. Area = (upper bottom+lower bottom) × height circle: perimeter = πd, area = πrr Cube: volume = side length× side length× side length cuboid: volume = length× width× height cylinder: bottom area× height cone: 1/3 Bottom area× height.