# Sine, cosine and tangent in a Unit Circle.

Using the applet below, you can explore how sin, cos and tan are defined in the part of the unit circle that lies in Quadrant I; as shown in the diagram below.
The next applet shows sin, cos and tan values for angles in all four quadrants. Use the slider to change the angle .
• Sin is the height of the right angle triangle and is represented by the blue segment.
• Cos ﻿ is the base of the right angle triangle and is represented by the red segment.
• Tan is the height of the brown segment where E is the intersection between the green ray and the tangent line at B.

a. In which Quadrant do you find the SUPPLEMENTS of Quadrant I angles? b. Use the diagram above to explore the relationship between SIN, COS and TAN of supplementary angles in Quadrant II and the related angle in Quadrant I. ﻿c. What rules can you write that connect SIN, COS and TAN of Quadrant I and III angles? d. How would you EXPLAIN why the relationships you have found between SIN, COS and TAN of angles in Quadrant I and Quadrant III make sense?