Activity
Texas Instruments

Texas Instruments: Angles Formed by Intersecting Chords, Secants, and Tangents

For Teachers 9th - 10th Standards
In this activity, students will investigate properties of angles and arcs formed when chords, secants, and tangents intersect and intercept arcs in a circle. They discover several important theorems concerning circles and arc sizes. They...
Graphic
Math2

Math2: Circles

For Students 9th - 10th Standards
This site has many useful formulas and examples relating to circles, including related definitions, circumference of a circle, area of a circle, length of a circular arc, area of a circular sector, equation of a circle in cartesian...
Activity
Math Open Reference

Math Open Reference: Circles

For Students 9th - 10th Standards
A complete reference guide to circles including parts, angles, and arcs. It provides definitions and interactive activities that enhance further explanation.
Activity
Lawrence Hall of Science

The Math Page: Trigonometry

For Students 9th - 10th Standards
Concepts in Trigonometry are explained and illustrated here by a member of the math department at Borough of Manhattan Community College.