# Trigonometric Definition with a Unit Circle.

- Author:
- kokming lee

- Topic:
- Circle, Trigonometry, 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.

1. Answer the following questions:
sin 10 degrees, cos 120 degrees, sin 120 degrees, tan120 degrees,
cos 230 degrees, sin 230 degrees, tan 230 degrees,
cos 350 degrees, sin 350 degrees, tan 350 degrees.
Compare your answers from the applet with that from a calculator.
2. Sine A is positive in which quadrants?
Cosine A is positive in which quadrants?
Tangent A is positive in which quadrants?