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Trigonometric Definition with a Unit Circle.

This applet shows how sine, cosine and tangent for an angle A is defined with a unit circle. Use the slider to see to change the angle A. Sin A is the height of the right angle triangle and is represented by the blue segment. Cos A is the base of the right angle triangle and is represented by the red segment. Tan A is the height of the brown segment where E is the intersection between the green ray and the tangent line at B.