May 18, 2015

Using coordinates, students prove that the intersection of the medians of a triangle meet at a point that is two-thirds of the way along each median from the intersected vertex.

Using coordinates, students prove the diagonals of a parallelogram bisect one another and meet at the intersection of the segments joining the midpoints of opposite sides.

Teacher and Student versions of full lesson from engageNY

- Mathematics > General
- Mathematics > Geometry

- Grade 9
- Grade 10

Reason abstractly and quantitatively.

Model with mathematics.

Use appropriate tools strategically.

Attend to precision.

Look for and make use of structure.

Use coordinates to prove simple geometric theorems algebraically.

Find the point on a directed line segment between two given points that partitions the segment in a given ratio.