Definition of 'altitude' and the various different ways the word is used in geometry
Math Open Reference

Gives examples of problems with intercepted arc, central angle, and angles inside and outside the circle.
Online Math Learning

Identify the missing angle measurement in each set of supplementary angles. Answers included.
MathDrills.com

Identify the missing angle measurement in each set of complementary angles. Answers included.
MathDrills.com

Explanation of acute angles
Math is Fun

Similar triangles  two sides in same proportion, included angle the same. SAS
Math Open Reference

In this Early Edge video lesson, you'll learn more about Triangles, so you can be successful when you take on highschool Math & Geometry.
The Princeton Review

Definition of a subtended angle  the angle created by an object at a given external point
Math Open Reference

Similar triangles  all three sides in same proportion. SSS
Math Open Reference

Definition of a segment of a circle.
Math Open Reference
