Ramanujans formula estimates the perimeter of a flat ellipse at p 3- Oe 3 a or about 3983379868 a instead of 4 a for a relative error of about -04155. Side side side side. Therefore in the case of a triangle the perimeter will be the sum of all the three sides.
They all get the perimeter of the circle correct but only Approx 2 and 3 and Series 2 get close to the value of 40 for the extreme case of b0.
In a rectangle the opposite sides of a rectangle are equal and so the perimeter will be twice the width of the rectangle plus twice the height of the rectangle. Therefore in the case of a triangle the perimeter will be the sum of all the three sides. Area is measured in square units such as square inches square feet or square meters. 2 length 2 width.