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. 2010 Sep 7;5(9):e12565. doi: 10.1371/journal.pone.0012565

Figure 1. Schematic representation of the 3D geometry and notations used.

Figure 1

The blue triangle (HIE) represents the left foot of the duck. The span of the foot is drawn as a thickened grey line (HM) that connects the base of the foot (H) with the tip of the mid digit (M). Grey area ABCD is the plane containing the span of the foot and the vector of velocity relative to water. Angles α and β are the angles between the velocity vector and the area of the foot (see text for further definitions). FN is hydrodynamic force normal to the foot that results from motion of the foot through water.