Khan Academy
Khan Academy: Example: Unit Circle Definition to Calculate Sin and Cos
Explains how to use the unit circle definition to calculate sin and cos of multiple angles. [15:26]
Khan Academy
Khan Academy: Example: Trig Function Values Using Unit Circle Definition
Worked example that uses the unit circle definition to evaluate trig functions. [11:24]
Khan Academy
Khan Academy: Algebra Ii: Trig Values of Special Angles: Triangle in Unit Circle
Sal finds the trigonometric values of pi/4 using the unit-circle definition. [7:53]