What is "polar curve"

A polar curve is a graph which contrasts the sink rate of an aircraft (typically a glider) with its horizontal speed.

In algebraic geometry, the first polar, or simply polar of an algebraic plane curve C of degree n with respect to a point Q is an algebraic curve of degree n−1 which contains every point of C whose tangent line passes through Q. It is used to investigate the relationship between the curve and its dual, for example in the derivation of the Plücker formulas.