Transformations Congruency
1. **State the problem:** Determine which sequences of transformations prove congruency by mapping polygon I onto polygon II.
2. **Analyze Shape Locations:** Polygon I is in quadrant I around points like (2,8), (10,10).
Polygon II is in quadrant III around points like (-12,-4), (-8,-6).
3. **Key idea:** To map I onto II, transformations must move from quadrant I to quadrant III (diagonally opposite).
4. **Transformation types:**
- Reflection across y-axis: flips x-coordinates sign.
- Rotation 90° CW: rotates points 90 degrees clockwise around origin.
- Rotation 90° CCW: rotates 90 degrees counterclockwise.
- Rotation 180°: rotates points 180 degrees.
- Translation moves points in specific directions.
5. **Check sequences:**
- a) Reflection across y-axis, then 90° CW rotation, then translate left 18 units.
-- Reflection across y-axis changes quadrant I points to quadrant II.
-- 90° CW rotation moves points from quadrant II to quadrant III.
-- Translation left 18 units shifts all points to the left.
-- This sequence can map shape I onto II, proving congruency.
- b) 90° CW rotation, then translate left 18 units.
-- 90° CW rotation moves quadrant I points to quadrant IV.
-- Translation left 18 units moves points left but does not move to quadrant III.
-- This does not map shape I onto shape II properly.
- c) 90° CCW rotation, reflection across y-axis, then translate left 18 units.
-- 90° CCW rotation moves quadrant I points to quadrant II.
-- Reflection across y-axis reflects quadrant II to quadrant I.
-- Overall, shape remains near quadrant I; translation left cannot move shape to III.
-- Does not prove congruency.
- d) 90° CW rotation, reflection across y-axis, then translate right 2 units.
-- 90° CW rotation moves quadrant I to quadrant IV.
-- Reflection across y-axis moves quadrant IV to quadrant III.
-- Translation right 2 units shifts shape slightly, still in quadrant III.
-- This sequence possibly maps I onto II, proving congruency.
- e) 180° rotation, reflection across y-axis, then 90° CW rotation.
-- 180° rotation moves quadrant I points to quadrant III.
-- Reflection across y-axis moves quadrant III to quadrant IV.
-- 90° CW rotation moves quadrant IV to quadrant I.
-- Result ends in quadrant I, so does not map to II.
- f) Reflection across y-axis, 90° CCW rotation, translate right 2 units.
-- Reflection across y-axis moves I to II.
-- 90° CCW rotation moves II to I.
-- Translation right 2 only small shift.
-- Does not map I onto II.
6. **Final classification:**
Sequences that prove congruency by mapping I onto II are (a) and (d).
**Answer:** The sequences (a) and (d) prove congruency by successfully mapping polygon I onto polygon II.