Welcome back to Bree’s Mathematical Blog! Today we will be exploring a Geometry Theorem called Two Secant Angle Theorem. This theorem states “if two lines intersect outside a circle, then the measure of an angle formed by the two lines is one half the positive difference of the measures of the intercepted arcs” (Angle of Intersecting Secants Theorem). What is cool about this theorem is it still holds if one or both of the secant lines are tangent lines. This theorem involves terms such as arcs, circles, and angles. The technology tool we will be using during our exploration is called GeoGebra. “GeoGebra is a dynamic mathematics software for all levels of education that brings together geometry, algebra spreadsheets, graphing, statistics, and calculus in one easy-to-use package” (About GeoGebra). This geometry software works great with today’s exploration. The best kind of proofs is one that helps you understand the meaning of the theorem being proved; to see not only that it is true, but also why it is true. So get ready to hop on the theorem exploration train, but be aware, it’s going to be moving fast.

For more information regarding  GeoGebra, click on the link.

Click on to the Theorem Solution for a break down of the Two Secant Angle Theorem.