## Lesson: Transformations Developing the Concept

Students have learned how to perform translations, rotations, and reflections. Now they will practice what they have learned.

Materials: overhead transparencies with coordinate grids on them, overhead washable pen, ruler; graph paper, ruler, and pencil for each student

Preparation: Four overhead grid transparencies with a trapezoid, a scalene triangle, a rectangle, and any other quadrilateral drawn on one of the five transparencies.

Prerequisite Skills and Background: Students should be familiar with various types of triangles and quadrilaterals. They should also have some familiarity with graphing points on a coordinate grid. Students should know the various types of angles and have an ability to use a ruler and protractor. They should also have knowledge of translations, rotations, and reflections.

• Say: Yesterday we learned about three transformations called translations, rotations, and reflections. Who can tell us what a translation does? (It moves figures along a straight line in one direction.)
Display an overhead grid transparency with a trapezoid drawn on it.
• Say: Yes, that's right. Who can tell us what kind of figure this is? (a trapezoid) Good, now who wants to show us how to translate this figure so that it moves three units to the right and four units down?
Have a volunteer do the translation on the overhead for the class to see.
• Say: That's great. What happens when we do a rotation? (We turn a figure about a given point.)
• Say: Let's try rotating a figure. Draw an isosceles triangle so that the non-congruent side is parallel to the bottom of the graph paper. (Give students a few minutes to make their drawings.) Label the triangle ABC with side AB parallel to the bottom of the paper and sides AC and BC the congruent sides. Now move two units to the left of point A and call that point P. Rotate the triangle 180 degrees counterclockwise about point P.