Fig. 1. Rotation angles. Rotation about the frog's center of mass can be resolved into rotations about three orthogonal axes. The origin of the axes is fixed to the animal's center of mass, and the axes themselves are fixed to the animal; the axes translate and rotate as the animal translates and rotates. (A) Rotation about the cranial—caudal axis is termed roll angle, ; rolling rotates the animal's right side up or down. (B) Rotation about a dorso-ventral axis is termed yaw angle, ; yawing rotates the animal's snout to the left or right. (C) Rotation about a lateral axis is termed angle of attack, ; pitching rotates the animal's snout up or down. Grey arrows indicate the directions of the indicated torques.