WilsonWorla 2 years ago The area of an ellipse is A = πab, but the perimeter cannot be expressed so simply: P≈ π(a+b)(3-(√(3a+b)(a+3b))/(a+b) ) prove that, when a=b=r, these become the familiar formulas for the area and perimeter of a circle

Try replacing all the b's with a. eg in the area: A = πab becomes $A = πaa = πa^2 = \pi r^2$ P will become: $P≈ π(a+a)(3-(√(3a+a)(a+3a))/(a+a) )$ now try simplifying that.