Rectangular S= length × width

Triangle S= base x height on base ÷2.

Parallelogram S= base x height on the base.

Trapezoidal S= (upper bottom+lower bottom) × height ÷2

Circle S= pi × radius?

Ellipse S= pi × length of long semi-axis × length of short semi-axis

Sector S= sector angle ÷360×π× radius? Or = arc length × radius /2

Cylinder S= bottom area × height

Cone s =1/3x (bottom area× height)

The arithmetic square root of triangle s =[P-A][P-B][P-C].

The circle is inscribed with the arithmetic square root of the quadrilateral S = [p-a] [p-b] [p-c] [p-d].

A, B, C, D are side lengths, and P is half the circumference.