Geometry
UNIT 1
Geometry Unit 1 Plan
Unit Number: 1
Unit Name: Constructions
Duration:
Standards Taught
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.

Learning Targets
1) Prove vertical angles are congruent.
2) Prove corresponding angles and alternate
interior angles are congruent when two
parallel lines are cut by a transversal and
converse.
3) Prove points on a perpendicular bisector
of a line segment are exactly equidistant
from the segments endpoint.
4) Use properties of congruence and
equality in various types of proofs as in twocolumn proofs, flow-chart proofs, and
paragraph proofs.
5) Encourage students to use precise
language to build logical arguments when
developing these proofs (MP.3 & MP.6)
G.CO.C.10 Prove theorems about triangles. 1) Prove the measures of interior angles of
Theorems include: measures of interior
a triangle sum up to 180⁰.
angles of a triangle sum to 180°; base angles 2) Prove that base angles of an isosceles
of isosceles triangles are congruent; the
triangle are congruent.
segment joining midpoints of two sides of a 3) Prove the medians of a triangle meet at a
triangle is parallel to the third side and half point.
the length; the medians of a triangle meet
4) Explore properties of triangles by using
at a point. 
tools such as tracing paper, compass &
straightedge, flow charts, and geometric
software for given situations.
G.CO.C.11 Prove theorems about
1) Prove opposite sides and opposite angles
parallelograms. Theorems include: opposite of a parallelogram are congruent.
sides are congruent, opposite angles are
2) Prove that diagonals of a parallelogram
congruent, the diagonals of a parallelogram bisect each other, and conversely,
bisect each other, and conversely,
rectangles are parallelograms with
rectangles are parallelograms with
congruent diagonals.
congruent diagonals. 
Make geometric constructions. 
G.CO.D.12 Make formal geometric
constructions with a variety of tools and
methods (compass and straightedge, string,
reflective devices, paper folding, dynamic
1) Copy and bisect a segment.
2) Copy and bisect an angle.
3) Use a variety of tools (i.e. dynamic
Geometry software and compass/
Geometry
geometric software, etc.). Copying a
segment; copying an angle; bisecting a
segment; bisecting an angle; constructing
perpendicular lines, including the
perpendicular bisector of a line segment;
and constructing a line parallel to a given
line through a point not on the line. 
G.CO.D.13 Construct an equilateral triangle,
a square, and a regular hexagon inscribed in
a circle. 
TASKS:
Resources:
UNIT 1
straightedge, patty paper, etc.) to perform
the following:
a. Construct perpendicular lines, including
the perpendicular bisector of a line
segment.
b. Construct a line parallel to a given line
through a point not on the line.
1) Construct an equilateral triangle so that
each vertex of the equilateral triangle is on
the circle.
2) Construct a square so that each vertex of
the square is on the circle.
3) Construct a regular hexagon so that each
vertex of the regular hexagon is on the
circle.
Geometry
Assessment:
UNIT 1