EngageNY
Circles, Chords, Diameters, and Their Relationships
A diameter is the longest chord possible, but that's not the only relationship between chords and diameters! Young geometry pupils construct perpendicular bisectors of chords to develop a conjecture about the relationships between chords...
EngageNY
Triangle Congruency Proofs (part 1)
Can they put it all together? Ninth graders apply what they know about proofs and triangle congruence to complete these proofs. These proofs go beyond the basic triangle congruence proofs and use various properties, theorems, and...
Illustrative Mathematics
Placing a Fire Hydrant
Triangle centers and the segments that create them easily become an exercise in memorization, without the help of engaging applications like this lesson. Here the class investigates the measure of center that is equidistant to the three...
Curated OER
Reflections and Equilateral Triangles
Your learners collaboratively find the lines of symmetry in an equilateral triangle using rigid transformations and symmetry. Through congruence proofs they show that they understand congruence in terms of rigid motions as they prove...
Curated OER
Special Segments in a Triangle
In this geometry worksheet, 10th graders review the vocabulary associated with the special segments of a triangle and the associated points of concurrency and solve problems in which they find the indicated missing angle or segment. The...
Curated OER
Isosceles Triangles
Young scholars identify the properties of an isosceles triangle. In this geometry instructional activity, students find the midpoint, median and angle bisector of a triangle. They construct angle bisectors and measure missing angles.
Curated OER
Math: Equal Area Triangles
Students examine a math worksheet and determine how to divide a single triangle into four of equal area. Using geometric principles, they sketch two additional ways to divide into into four equal triangles. To conclude, students...