Ellipse circumference and area _ from a foreigner's homework paper

High school took so long analytic geometry, turned over so long conic section, incredibly did not consider the perimeter area of the ellipse, it is a sin sin, in fact, the area is considered, the length of the irrational commutes becomes a circle area formula.

Today saw a foreigner's homework paper, the contents are as follows:

The first paragraph is to introduce our familiar Triangle Helen Formula, and then do a deformation, the latter part of the shape of Helen with a similar formula to tell the circumference of the ellipse and area. Then the special case of the cobblestone ellipse, the same as the length of the week.

The perimeter formula that we use here is:

Of course, he says this is an approximate formula, and there's a more precise formula:

Area of course is pi*a*b.

Ellipse circumference and area _ from a foreigner's homework paper