Geometry 4.1 Congruent Figures

Congruent Figures Two objects are congruent ( ) if they have the same size and shape Two figures are congruent if and only if their vertices can be matched up so that corresponding parts (angles and sides) of the figures are congruent. When writing which figures are congruent, be sure to write the vertices in the same order.

A R B C S T Triangle ABC Triangle RST

A R B C S T Triangle ABC Triangle RST

D M A J B C K L Quadrilateral ABCD Quadrilateral JKLM

D M A J B C K L Quadrilateral ABCD Quadrilateral JKLM

Congruent Figures Sometimes you have to change the position of the figures to match up vertices Practice “spinning” and “sliding” the figures mentally

SPIN and SLIDE

Defn. of Congruent Triangles Two triangles are congruent ( ) if and only if their vertices can be matched up so that the corresponding parts (angles and sides) of the triangles are congruent. A E D F B C

Defn. of Congruent Triangles Two triangles are congruent ( ) if and only if their vertices can be matched up so that the corresponding parts (angles and sides) of the triangles are congruent. ∆ ABC ∆ DEF A 7 7 D The order must match. B 7 7 E A D C 7 7 F AB DE BC EF B C E F CA FD

CPCTC When the definition of congruent triangles is used in a proof, use the wording: “corresponding parts of congruent triangles are congruent” CPCTC

Name 3 pairs of corresponding sides. Name 3 pairs of corresponding angles. Is it correct to say M A B N O Y ?

Complete the statements given . B D A Why is ?

Name the coordinates of B, I, and G. P Name the coordinates of B, I, and G. Name the coordinates of a point D, such that . Name the coordinates of a point O, such that .

Homework pg. 120 #1-6, 10-13, (15-21 odd) Makeups next week are Wednesday after school Graphing Calculator?