Isosceles and Equilateral Triangles
Grade 10 · Math · 90 min· Savvas Envision Geometry
What's Included
Learning Objective
I can apply properties of isosceles and equilateral triangles to determine unknown angle measures and side lengths.
Warm-Up Video
Khan Academy · 6:27
Equilateral and isosceles example problems | Congruence | Geometry | Khan Academy
Guided Notes
3 key concepts
- 1
In an isosceles triangle, the two base angles are congruent, meaning they have the same measure.
- 2
If all three sides of a triangle are congruent, then all three angles are congruent and each angle measures 60 degrees, making it an equilateral triangle.
- 3
If two sides of a triangle are congruent, the angles opposite those sides are congruent, and the sum of all angles in the triangle equals 180 degrees.
Practice Questions
12 questions · Multiple choice & Short answer
Exit Ticket
Quick comprehension check
“Triangle PQR is isosceles with PQ = PR. If angle P measures 28°, find the measure of angle Q.”
Complete Lesson Package
Get all 3 ready-to-use resources:
