Congruent Figures (8-9)

Congruent Figures

Vocabulary

Side-Side-Side Rule- all sides and angles of two polygons are congruent.

Congruent- having exactly the same size and shape.

Similar- figures that have the same shape, but not necessarily the same size.

Examples

Two polygons are congruent if they are the same size and shape - that is, if their corresponding angles and sides are equal.

Congruent

If one shape can become another using Turns, Flips and/or Slides, then the shapes are Congruent:

Rotation		Turn!
Reflection		Flip!
Translation		Slide!

After any of those transformations (turn, flip or slide), the shape still has the same size, area, angles and line lengths.

Examples

These shapes are all Congruent:

Rotated	Reflected and Moved	Reflected and Rotated

Congruent or Similar?

The two shapes need to be the same size to be congruent.
When we need to resize one shape to make it the same as the other, the shapes are Similar.

When we ...		Then the shapes are ...
... only Rotate, Reflect and/or Translate		Congruent
... also need to Resize		Similar

Congruent? Why such a funny word that basically means "equal"? Probably because they would only be "equal" if laid on top of each other. Anyway it comes from Latin congruere, "to agree". So the shapes "agree"
http://www.mathsisfun.com/geometry/congruent.html

Video Help

https://www.youtube.com/watch?v=CUKDzC5f6B4

https://www.youtube.com/watch?v=ZELWgQiiHSE

https://www.youtube.com/watch?v=0mKmYxuMirE