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According to the CCSS, students first investigate congruence formally in the eighth grade. This do now is both a diagnostic and a review. Students are shown five triangles and asked which triangles are congruent to each other. The triangles each have two given sides lengths and angle measures. Using the given information students identify which triangles have the three equal sides and three equal angles.

In order to identify which pairs of triangles are congruent, students need to build on prior knowledge about the sum of the measures of the interior angles in a triangle, isosceles triangles and then Pythagorean theorem.

The question in the Do Now asks students to identify congruent triangles, but not explain why the triangles are congruent. When we go over the Do Now, I ask students to explain how they know the triangles are congruent.

Some students may need a brief reminder of the definition of "congruent" and further explanation about how to find the missing side lengths and angle measures.

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According to the CCSS, students first investigate congruence formally in the eighth grade. This do now is both a diagnostic and a review. Students are shown five triangles and asked which triangles are congruent to each other. The triangles each have two given sides lengths and angle measures.

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Website with Video

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In this video you will learn what isometry is and how it applies to transformations in geometry.

Isometry: Used to describe a transformation where the size and orientation are maintained.
Direct Isometry: Orientation stays the same.
Opposite Isometry: Orientation is reversed.

Direct Isometry:
In a transformation, a direct isometry, the order of the points are constant before and after the transformation. In a translation, for example, the order of points stays the same, so it is a direct isometry.

Direct Isometry can be found in: Translations, Point Reflections, and Rotations

Opposite Isometry:
In a line reflection, however, an opposite isometry is present and not the direct isomertry. The flipping of the pre-image over a given line reverses the orientation of the image, so it is an opposite isometry.

Opposite Isometry can be found in: Line Reflections

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In this video you will learn what isometry is and how it applies to transformations in geometry. Isometry: Used to describe a transformation where the size and orientation are maintained. Direct Isometry: Orientation stays the same. Opposite Isometry: Orientation is reversed.

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An isometry is a rigid transformation.

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Transformations and Isometries - Concept - Geometry Video by Brightstorm

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Time-saving video that describes all the different types of transformations in Geometry: dilations, rotations, translations, and reflections. Isometry is also described. Concept explanation.

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Website that States and Defines Rigid Motions 

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Website that States and Defines Rigid Motions 

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Any way of moving all the points in the plane such that a) the relative distance between points stays the same and b) the relative position of the points stays the same. There are four types of rigid motions that we will consider: translation , rotation, reflection, and glide reflection.