Triangle Slices
Unit 4 ● Lesson 3 ● Activity 1
Sketch an equilateral triangle and an altitude from any vertex in the equilateral triangle.
What do you notice? What do you wonder?
Slides are CC BY NC Kendall Hunt Publishing. Curriculum excerpts are CC BY Illustrative Mathematics.
Warm-up: Notice and Wonder
Half an Equilateral Triangle
Unit 4
Lesson 3
Right Triangle Trigonometry
GEOMETRY
Unit 4 ● Lesson 3
I can determine the side lengths of triangles with 30, 60, and 90 degree angles.
Learning
Targets
Geometry
Decomposing Equilateral Triangles
Unit 4 ● Lesson 3 ● Activity 2
Here is an equilateral triangle with side length 2 units and an altitude drawn. Find the values of x and y.
Slides are CC BY NC Kendall Hunt Publishing. Curriculum excerpts are CC BY Illustrative Mathematics.
Decomposing Equilateral Triangles
Unit 4 ● Lesson 3 ● Activity 2
Slides are CC BY NC Kendall Hunt Publishing. Curriculum excerpts are CC BY Illustrative Mathematics.
Half an Equilateral Triangle
Unit 4 ● Lesson 3
In half an equilateral triangle (aka 30-60-90 triangle), the hypotenuse is twice the length of the shorter leg. The longer leg is the shorter leg times the square root of 3.
Slides are CC BY NC Kendall Hunt Publishing. Curriculum excerpts are CC BY Illustrative Mathematics.
Lesson Synthesis
Generalize Half Equilateral Triangles
Unit 4 ● Lesson 3 ● Activity 2
Calculate the lengths of the unlabeled sides.
Slides are CC BY NC Kendall Hunt Publishing. Curriculum excerpts are CC BY Illustrative Mathematics.
Half of the Half
Unit 4 ● Lesson 3 ● Activity 4
Calculate the lengths of the 2 unlabeled sides.
Slides are CC BY NC Kendall Hunt Publishing. Curriculum excerpts are CC BY Illustrative Mathematics.
Lesson Synthesis
Cool-down