Can anyone tell me the formula for calculating the circumference of an ellipse? Can you explain it more clearly? When the major axis is 50 and the minor axis is 20, what is its circumference? What does each letter mean?,,,

Can anyone tell me the formula for calculating the circumference of an ellipse? Can you explain it more clearly? When the major axis is 50 and the minor axis is 20, what is its circumference? What does each letter mean?,,,

The exact calculation of the circumference of an ellipse (L) requires the summation of integrals or infinite series
(0 - pi / 2) integral of L = 4A * sqrt (1-e ^ sin ^ t), where a is the major axis of the ellipse and E is the eccentricity
For approximate calculation, the following formula can be used:
L = pi (1.5 (a + b) - sqrt (AB)), where a and B are major axis and minor axis of ellipse respectively
L＝（a+b）*180°*(（a-b）/a)/arctg((a-b)/a)
(a＞0,b≥0,b→a)
When B → a, ellipse → circle
L = 2A π or L = 2R π
When B = 0, ellipse = straight line
L＝4a
In ellipse formula, semimajor axis A and semiminor axis B are interchangeable