Honors Geometry Section 4.1 Congruent Polygons

To name a polygon, start at any vertex and go around the figure, either clockwise or counterclockwise , and name the vertices in order.   Example 1: Give two (out of 12) possible names for the hexagon at the right. DEMONS MEDSNO

In simple terms, two polygons are congruent if they have exactly the same size and shape.

More formally, two polygons are congruent iff their vertices can be paired so that corresponding angles and sides are congruent.

Example 2. List the congruent sides and angles in the quadrilaterals below.

When naming congruent polygons, you must list the corresponding vertices in order. This is known as a congruence statement.

Example 3: Complete this congruence statement using the figure above: quad GONE quad ____ YATS

By looking at a congruence statement, you can determine the pairs of corresponding parts.   Example 4: Use the statement to fill in the blanks.

To prove two triangles are congruent using the definition of congruent polygons, one must show that all 6 pairs of corresponding parts are congruent.

----------------------------------------- Given Isosceles Triangle Theorem Definition of Midpoint Def. of Perpendicular Lines Right Angle Theorem Def. of Angle Bisector Reflexive Property Def. of cong. polygons

In subsequent sections, you will see that it is possible to prove that some triangles are congruent by using only three pairs of congruent parts!