Other
Dans Math: Lessons: Calculus (Part 1)
College professor Dan Bach reviews the basic calculus concepts of limits and derivatives. The site includes examples and animated graphs.
Texas Instruments
Texas Instruments: Drawing a Line Tangent to a Circle
Students use the drawing and measurement tools of Cabri Jr. to draw a line tangent to a circle. [Requires Adobe Reader.]
Cut the Knot
Cut the Knot!: Monge's Theorem of Three Circles and Common Tangents
Very good site presenting a Trig problem dealing with tangents lines and circles, then linking the student to the solution
Paul Dawkins
Paul's Online Notes: Calculus I: Limits
Learners explore limits. Topics investigated are continuity, limits at infinity, limit properties, tangent lines, and rates of change. Class notes, definitions, and examples with detailed solutions are included. The class notes are...
CK-12 Foundation
Ck 12: Geometry: Properties of a Circle Study Guide
[Free Registration/Login may be required to access all resource tools.] This study guide reviews the terminology for circles (tangent, arcs, central angles) and the equation for a circle.
Cool Math
Coolmath: More on Tangent Lines
This CoolMath resource provides instruction and practice for tangent lines.
National Council of Teachers of Mathematics
Nctm: Illuminations: Interactive Calculus Tool
Investigate graphs of polynomial functions, tangent lines, derivatives, and area under a curve with this interactive applet.
Shodor Education Foundation
Shodor Interactivate: Derivate
View the graph and the equation of the line tangent to any function at any point on the function.