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Geometric Twins

One line, one corner

Hold up two threads, one straight and one slanted. Pull both tight. They are the same length.

Look at each pair. Say yes or no.

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Tilt and arm length can differ. Length and degrees cannot.

The test on one thing

A line segment is part of a line, with two end points. An angle is two arms that start at one point. An arm is a straight line.

  • Two line segments are congruent when their lengths are equal.
  • Two angles are congruent when their sizes in degrees are equal.

Tilt is how much a line slants. It does not matter. Turning a segment does not change its length. An angle's size is the turn between its arms. It is not how long the arms are drawn.

What must match
FigureWhat must match
Line segmentIts length
AngleIts size in degrees
CircleIts radius
RectangleIts length and its width

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This track

  1. 0 Start here
  2. 1 Landing one on the other
  3. 2 Slide it, turn it, flip it
  4. 3 A bigger copy is a different figure
  5. 4 One line, one corner
  6. 5 Three sides settle it
  7. 6 Two sides and the corner between them
  8. 7 Two corners and a side
  9. 8 When shape is not enough
  10. 9 Writing a congruence in order
  11. 10 RHS: a right angle, the hypotenuse, a side
  12. 11 Equal sides, equal angles
  13. 12 Twins hiding in a figure
  14. 13 Checkpoint: order, RHS and angles
  15. 14 The big picture
  16. 15 Track quiz

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