Surface of revolution

Hi there, basically I want to create a an egg shape, chopped in half, so pointy end to a circle in 3D. So I need to define a curve, which has a gradient of up1 and across 1. Then I will rotate it around the y axis 360 degrees.

How do i define such a curve through the magic of maths? I know the height of is 0.4 and the radius 0.2, so yeh 1:1. But it has to be a curve