Ellipse Area
An ellipse is the intersection of a plane and a circular cylinder.
Since two radii of circles are involved in the graphical creation of an ellipse – minor and major, or as they are also called for the ellipse – minor and major semi-axis, they naturally participate in the calculation of the area.
A circle is a special case of an ellipse. Along with the hyperbola and parabola, the ellipse is a conic section and a quadric.
Ellipse area – is the part of the surface that is bounded by the closed lines of this figure.
The formula used to calculate the area of an ellipse: 
Where pi – is the constant number 3.1415, a - denotes the value of the major semi-axis, b- is the length of the minor semi-axis.
To your attention, an animation on how to draw an ellipse.