Isosceles and Equilateral Triangles
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Objective
I can apply properties of isosceles and equilateral triangles to determine unknown angle measures and side lengths.
Part 1 of 4
Warm-up video
Khan Academy · 6:27Vetted channel
We don't generate video — this one is by Khan Academy on YouTube. The practice questions and exit ticket below were drafted by AI for this objective, and every question is editable in the teacher guide.
Part 2 of 4
Key concepts
3 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.
Part 3 of 4
Practice
12 questions
In an isosceles triangle, two sides are congruent. What term is used to describe the angle formed by these two congruent sides?
Triangle PQR is isosceles with PQ = PR. If angle P measures 40 degrees, find the measure of angle Q.
Part 4 of 4
Exit ticket
Quick comprehension check
“Triangle PQR is isosceles with PQ = PR. If angle P measures 28°, find the measure of angle Q.”
Sample answer included in the free materials
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