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Transcript
Triangle Congruence
Proving Triangles Congruent
Side-Side-Side (SSS) Postulate
Side-Angle-Side (SAS) Postulate
Non-example of SAS
• Why can’t we use SAS to show these triangles
congruent?
• The angle in the second triangle is not
between the two sides! Not SAS!
Angle-Side-Angle (ASA) Postulate
Assumptions
• Sometimes we have to mark assumptions
• Assumptions are things that we know are
true, but the figure might not immediately
give us this information for free – we have to
think about it!
Assumption #1 – Reflexive Property
• If two triangles share a side, that side is
congruent to itself!
• SSS
Assumption #2 – Third Angle
• If two pairs of corresponding angles are
congruent, then the third pair is also congruent!
• Why? Triangle Angle Sum Theorem says the
measures of the angles have to sum to 180!
• ASA
Assumption #3 – Vertical Angles
• Vertical angles are congruent!
• ASA
Assumption #4 – Third Side of a RIGHT
Triangle
• If two pairs of corresponding sides are congruent
in a RIGHT TRIANGLE, then the third pair is also
congruent!
• Why? Pythagorean Theorem states that
a2+b2=c2. This can only be true if a, b, and c are
the same in both triangles.
• SSS