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Proving Triangles Congruent. F. B. A. C. E. D. The Idea of a Congruence. Two geometric figures with exactly the same size and shape. How much do you need to know. . . . . . about two triangles to prove that they are congruent?.
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F B A C E D The Idea of a Congruence Two geometric figures with exactly the same size and shape.
How much do you need to know. . . . . . about two triangles to prove that they are congruent?
Corresponding Parts • AB DE • BC EF • AC DF • A D • B E • C F B A C E F D You learned that if all six pairs of corresponding parts (sides and angles) are congruent, then the triangles are congruent. ABC DEF
SSS SAS HL ASA AAS Do you need all six ? NO !
Side-Side-Side (SSS) B E F A C D • AB DE • BC EF • AC DF ABC DEF
Side-Angle-Side (SAS) B E F A C D • AB DE • A D • AC DF ABC DEF included angle
Included Angle The angle between two sides H G I
E Y S Included Angle Name the included angle: YE and ES ES and YS YS and YE E S Y
Hypotenuse Leg (HL) E A F C B D • AB DE • BE • AC DF ABC DEF right angle
Angle-Side-Angle (ASA) B E F A C D • A D • AB DE • B E ABC DEF included side
GI GH HI Included Side The side between two angles
E Y S Included Side Name the included side: Y and E E and S S and Y YE ES SY
Angle-Angle-Side (AAS) B E F A C D • A D • B E • BC EF ABC DEF Non-included side
Warning: No SSA or ASS Postulate There is no such thing as an SSA or ASS postulate! E B F A C D NOT CONGRUENT
Warning: No AAA Postulate There is no such thing as an AAA postulate! E B A C F D NOT CONGRUENT
SSS • SAS • HL • ASA • AAS • SSA or ASS • AAA The Congruence Postulates
Name That Postulate (when possible) SAS ASA SSA SSS
Name That Postulate (when possible) AAA ASA SSA SAS
Name That Postulate (when possible) Vertical Angles Reflexive Property SAS SAS Reflexive Property Vertical Angles SSA SAS
Name That Postulate (when possible) none Reflexive Property SSS SSA AAA
Name That Postulate (when possible) Reflexive Property SSA Vertical Angles ASA SAS
Let’s Practice ACFE Indicate the additional information needed to enable us to apply the specified congruence postulate. For ASA: B D For SAS: AF For AAS:
Try it! MKTU Indicate the additional information needed to enable us to apply the specified congruence postulate. N V For ASA: For SAS: M U For AAS: