Sines (beware units in questions!) An animation presenting the relationship between the sine function and the chords in the first quadrant with links to exercises and answers
Cosines (beware units in questions!) An animation presenting the relationship between the cosine function and the chords in the first quadrant with links to exercises and answers (Java Applet)
Tangents An animation presenting the relationship between the tangent function and the chords in the first quadrant with links to exercises and answers (Java Applet)