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MCC9-12.G.CO.7
• MCC9-12.G.CO.7 Use the definition of
congruence in terms of rigid motions to show
that two triangles are congruent if and only if
corresponding pairs of sides and
corresponding pairs of angles are congruent.
What’s the Big Idea?
• Two triangles are said to be congruent if one
can be exactly superimposed on the other by
a rigid motion.
• In a pair of congruent triangles, corresponding
sides are congruent and corresponding angles
are congruent
• In other words matching angles and sides.
Grade Level Example
• Students identify corresponding sides and
corresponding angles of congruent triangles.
• Explain that in a pair of congruent triangles,
corresponding sides are congruent and
corresponding angles are congruent.
• Demonstrate that when distance is preserved
(corresponding sides are congruent) and angle
measure is preserved (corresponding angles are
congruent) the triangles must also be congruent.
Adapted from Illustrative Mathematics G.CO.8 Why does SSS Work?
Grade Level Example
• Are the following triangles congruent? Explain
how you know.
MCC9-12.G.CO.7
Unpacking the Standards
• Use the definition of congruence in terms of
rigid motions to show that two triangles are
congruent if and only if corresponding pairs of
sides and corresponding pairs of angles are
congruent.
Access Examples
• Identify corresponding congruent parts of two
triangles.
• Match triangles by matching congruent sides
and angles.
• Choose matching triangle from a choice of
two or more, and only one has corresponding
sides and angles.
Access Example
• In making a kite, which triangles on the kite
will match this triangle? Student must match
the correct sides and angles.