Relate Adjacent Parallelogram Angles
Opposite parallelogram sides are parallel.
About 20 minutes, plus any extended practice
Open lesson 1Geometry: Quadrilaterals and Coordinate Reasons
Geometric properties can be expressed through coordinates as well as diagrams. Parallelogram angle and diagonal theorems, midpoint coordinates, perpendicular slopes and perpendicular base-height relationships provide exact arguments about figures.
Before you begin
- Evaluate midpoint averages and signed fractions; know parallelograms and triangle area.
Choose by skill rather than age alone. Read with an adult when useful, revisit a lesson, or explore another grade.
Follow the lesson sequence
Locate Where Parallelogram Diagonals Meet
Parallelogram diagonals bisect one another.
About 20 minutes, plus any extended practice
Open lesson 2Use a Negative Reciprocal to Test a Right Angle
Two nonvertical perpendicular lines have slope product negative one.
About 20 minutes, plus any extended practice
Open lesson 3Use Perpendicular Coordinate-Axis Legs
A triangle with legs along the coordinate axes has an explicit right angle at their meeting point.
About 20 minutes, plus any extended practice
Open lesson 4Review and transfer
After the lessons, try 4 new review cases and a practical task. Each answer has an explanation and a link back to the related lesson.
Open the unit reviewGuest answers are temporary. Keep your own paper or document; this unit does not certify completion or record a school grade.
Topic references
- California CCSS mathematics topic reference: topic reference — Geometry: Quadrilaterals and Coordinate Reasons
These references informed the topic selection. They do not certify complete standards alignment.