The contrapedal curve, also called a normal pedal curve, is defined analogously to a usual pedal curve with "tangent" replaced
by "normal." In particular, the contrapedal curve of a curve is the locus of bases of perpendiculars let down to normal
lines of .
The contrapedal curve is the pedal curve of the evolute of a given curve (Zwikker 1963, p. 151).
of a curve 
is the locus of bases of perpendiculars let down to normal
lines of 
.
