Download G-CO.C.9

Mathematics Curriculum Supplement
Geometry (G-CO.C.9)
Geometry
Mathematics
Highly-Leveraged Standard1
G-CO.C.9 Prove theorems about lines and angles. Theorems include: vertical angles are congruent; when a transversal
crosses parallel lines, alternate interior angles are congruent and corresponding angles are congruent; points on a
perpendicular bisector of a line segment are exactly those equidistant from the segment’s endpoints.
Student Learning Targets:
Students will be able to:
 explain the angle relationships found when two lines are cut by a transversal, including alternate interior angles,
alternate exterior angles, corresponding angles, and same-side interior angles.
 explain the relationships between pairs of angles, including vertical angles, supplementary angles,
complementary angles, and linear pairs.
 prove relationships between pairs of angles including all right angles are congruent, supplements to the same
angle are congruent and vertical angles are congruent.
 prove congruent angle relationships concerning parallel lines intersected by a transversal including alternate
interior angles, alternate exterior angles, same-side interior angles and same-side exterior angles.
 prove points on a perpendicular bisector of a line segment are exactly equidistant from the segment's endpoints.
Performance Level Descriptors
Standard
Minimally Proficient
Partially Proficient
Proficient
Highly Proficient
The Minimally
The Partially Proficient
The Proficient student
The Highly Proficient
Proficient student
student
student
Congruence
G-CO.C [9] Describes examples of
Determines the validity
Proves theorems about
Applies theorems about
theorems about lines and of statements within a
lines and angles.
lines and angles to a
angles.
given proof of a theorem
real-life context.
about lines and angles.
1
Highly-Leveraged Standards are the most essential for students to learn because they have endurance, leverage and essentiality.
This definition for highly-leveraged standards was adapted from the website of Millis Public Schools, K-12, in Massachusetts, USA.
http://www.millis.k12.ma.us/services/curriculum_assessment/brochures
Specifically for mathematics, the Highly-Leveraged Standards are the Major Content/Clusters as defined by the AZCCRS Grade
Level Focus documents. They should encompass a range of at least 65%-75% for Major Content/Clusters and a range of 25%-35%
for Supporting Cluster Instruction. See the Grade Level Focus documents at:
https://cms.azed.gov/home/GetDocumentFile?id=57069f7baadebe0bccd0a8b5
TUSD Department of Curriculum and Instruction
Curriculum 3.0
Revised 4/29/2017 3:43 AM
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