The lecture introduces isometries in the plane, focusing on their definition, properties, and examples. It explains how isometries preserve distances and discusses their role in geometry. The lecture also covers the composition of isometries, forming a group structure, and explores subgroups within isometries, providing examples like central symmetry and reflection.

What is the primary focus of geometry as discussed in the lecture?

• Studying the material of figures

• Studying the distance of figures from the board

• Studying properties of figures invariant under transformations

• Studying the color of figures

Which of the following is a key property of an isometry?

• It changes the size of figures

• It modifies the color of figures

• It preserves distances between points

• It alters the angles of figures

What is a central symmetry in the context of isometries?

• A transformation that scales a figure

• A transformation that reflects a figure through a central point

• A transformation that translates a figure

• A transformation that rotates a figure

How does a reflection as an isometry affect a figure?

• It scales the figure

• It rotates the figure

• It reflects the figure across a line

• It translates the figure

Which of the following is preserved by isometries?

• The color of the figure

• The material of the figure

• The distance between points

• The weight of the figure

What does it mean for isometries to form a group?

• They can be divided

• They can be composed to form another isometry

• They can be added together

• They can be subtracted

What is a subgroup in the context of isometries?

• A set of isometries that includes only rotations

• A set of isometries that itself forms a group

• A set of isometries that includes only reflections

• A set of isometries that includes only translations