alleryCombining two reflections about lines through the origin gives which motion?
AA reflection
BA scaling
CA shear
DA rotation
Answer & Solution
Correct answer: D. A rotation
1. Each reflection matrix has determinant -1.
2. Multiplying two of them gives determinant +1, a special orthogonal matrix.
3. Such a matrix represents a rotation, not another reflection, a scaling or a shear.
_Source: Wikipedia, Reflection (mathematics), section Properties_
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