# ALEX Classroom Resources

ALEX Classroom Resources
Subject: Mathematics (9 - 12), Mathematics (9 - 12)
Title: Geometry Module 5, Topic A: Central and Inscribed Angles
URL: https://www.engageny.org/resource/geometry-module-5-topic-a-overview
Description:

Module 5, Topic A leads students first to Thales' theorem (an angle drawn from a diameter of a circle to a point on the circle is sure to be a right angle), then to possible converses of Thales' theorem, and finally to the general inscribed-central angle theorem. Students use this result to solve unknown-angle problems. Through this work, students construct triangles and rectangles inscribed in circles and study their properties.

Subject: Mathematics (9 - 12), Mathematics (9 - 12)
Title: Geometry Module 5, Topic B: Arcs and Sectors
URL: https://www.engageny.org/resource/geometry-module-5-topic-b-overview
Description:

Module 5, Topic B defines the measure of an arc and establishes results relating to chord lengths and the measures of the arcs they subtend. Students build on their knowledge of circles from Module 2 and prove that all circles are similar. Students develop a formula for arc length in addition to a formula for the area of a sector and practice their skills solving unknown area problems.

Subject: Mathematics (9 - 12), Mathematics (9 - 12)
Title: Geometry, Module 5, Topic C: Secants and Tangents
URL: https://www.engageny.org/resource/geometry-module-5-topic-c-overview
Description:

In Module 5, Topic C, students explore geometric relations in diagrams of two secant lines, or a secant and tangent line (possibly even two tangent lines), meeting a point inside or outside of a circle. They establish the secant angle theorems and tangent-secant angle theorems. By drawing auxiliary lines, students also notice similar triangles and thereby discover relationships between lengths of line segments appearing in these diagrams.

ALEX Classroom Resources: 3