Performing and Sequencing Rigid Transformations
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Geometry › Performing and Sequencing Rigid Transformations
Triangle $DEF$ is mapped onto triangle $D'E'F'$ on the coordinate plane by two rigid transformations. Order matters. Which description correctly orders the transformations?
Translate up 3 units, then rotate $90^\circ$ clockwise about the origin.
Rotate $90^\circ$ clockwise about the origin, then translate up 3 units.
Rotate $90^\circ$ clockwise about the origin only.
Rotate $90^\circ$ counterclockwise about the origin, then translate up 3 units.
Explanation
This is a sequencing rigid transformations problem where we need to map triangle DEF onto triangle D'E'F'. The transformations needed are a rotation and a translation. The order matters significantly because rotations about the origin change both orientation and position. The correct sequence is to rotate 90° clockwise about the origin first, then translate up 3 units. This works because the rotation reorients the triangle and moves it to a new position relative to the origin, then the translation shifts it up to the final location. If we translated up first then rotated (choice B), the triangle would end up in the wrong position because rotation about the origin would move the already-elevated triangle in a circular path. The key principle is to perform rotations about the origin before translations to achieve the desired final position.
On the coordinate plane, triangle $RST$ is mapped onto triangle $R'S'T'$ using two rigid transformations. Order matters. Which description correctly orders the transformations?
Translate down 2 units only.
Rotate $90^\circ$ clockwise about the origin, then translate down 2 units.
Rotate $90^\circ$ counterclockwise about the origin, then translate down 2 units.
Translate down 2 units, then rotate $90^\circ$ counterclockwise about the origin.
Explanation
This is a sequencing rigid transformations problem where we need to map triangle RST onto triangle R'S'T'. The transformations needed are a rotation and a translation. The order matters because rotations about the origin affect both position and orientation. The correct sequence is to rotate 90° counterclockwise about the origin first, then translate down 2 units. This works because the rotation reorients the triangle and moves it to a new position around the origin, then the translation shifts it down to reach the final location. If we translated down first then rotated (choice B), the lowered triangle would follow a circular path during rotation and end up in the wrong position. The key principle is to perform rotations about the origin before translations to ensure the correct final placement.