The professor describes three basic transforms: Rotation, Scaling, and Translation. The official definition describes a fourth, rotation, which is not introduced until it is included among the linear transforms (including shear, which is not basic); thinking back it seems cannot be accomplished by any of the other transforms. For example, rotating a right hand in the first quadrant 90 degrees (counterclockwise) puts the hand in the second quadrant, but does not actually make it a left hand (reflect it across the y-axis); similarly, scaling by -1 (if you allow negative scaling which goes past the origin) does not reflect either, the handedness is preserved.
The professor describes three basic transforms: Rotation, Scaling, and Translation. The official definition describes a fourth, rotation, which is not introduced until it is included among the linear transforms (including shear, which is not basic); thinking back it seems cannot be accomplished by any of the other transforms. For example, rotating a right hand in the first quadrant 90 degrees (counterclockwise) puts the hand in the second quadrant, but does not actually make it a left hand (reflect it across the y-axis); similarly, scaling by -1 (if you allow negative scaling which goes past the origin) does not reflect either, the handedness is preserved.