Learn a couple of useful isosceles triangle properties as discovered with a compass and straightedge.

Objective 1a

You will be able to develop and prove theorems about isosceles triangles. In this video, we discuss Pons Asinorum and the definition of an isosceles triangle. Duration_8_49

Isosceles Triangle Construction

This video will demonstrate how to quickly and intuitively construct an isosceles triangle using a compass and straight edge. Duration_1_40

Objective 1b

Investigate the Base Angles Theorem using a protractor or various paper folding techniques, then follow my lead as I guide you across the notorious Pons Asinorum. Watch your step, as this bridge has quite the reputation for producing casualties. Duration_25_45

Objective 1c

Here, we will examine two simplified proofs of the Base Angles Theorem involving medians and altitudes. We’ll also work through a handful of examples (Ex 3 through Ex 6) using the Base Angles Theorem. Duration_11_53

Objective 1d

This video discusses the set up for investing the Converse of the Base Angles Theorem. Ready your compass and straightedge! Duration_2_31

Compass and Straightedge Investigation

Use your trusty compass and straightedge to investigate the Converse of the Base Angles Theorem. Duration_5_03

Objective 1e

In this video, we will formally state the Converse of the Base Angles Theorem, discuss its proof, and demonstrate that an equilateral triangle is also equiangular. Duration_13_05

Objective 1f

Within this digital container, you will find a variety of examples (Ex 7 through Ex 10) that use the Equilateral Triangle Theorem, the Base Angles Theorem, Triangle Sum Theorem, and even the Triangle Exterior Angle Theorem. As if that as insufficient, we’ll also throw in some alternate interior angles for good measure. Duration_9_38

Geometry 5(A) investigate patterns to make conjectures about geometric relationships, including angles formed by parallel lines cut by a transversal, criteria required for triangle congruence, special segments of triangles, diagonals of quadrilaterals, interior and exterior angles of polygons, and special segments and angles of circles choosing from a variety of tools

Geometry 6(D) verify theorems about the relationships in triangles, including proof of the Pythagorean Theorem, the sum of interior angles, base angles of isosceles triangles, midsegments, and medians, and apply these relationships to solve problems