Lesson Materials

Lesson 8-1: Trig Parent Graphs

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now)

Objective:

The student will be able to graph the parent graphs of all 6 trig functions.

1. Dragging the red dot (labeled "DRAG") will change the angle, alpha, in the unit circle. Drag this point left and right. The angle alpha is in standard position, but notice that the figure shows the reference angle too!
2. As the angle changes, the point (alpha, y) is being plotted to the right of the unit circle. When alpha = 0, y = 0 so we see the point (0, 0) on the graph. Remember, the y-coordinate on the unit circle is the SINE of the angle!
3. Look for SINE values that you know, for instance, what is the sine of 90° (pi over 2 radians or approximately 1.57 radians)? Look for the y-coordinate on the graph above alpha = 1.57. How about the sine of 180° (3.14 radians) or 270° (4.71 radians)? Do you see a pattern?
1. Elementary Trigonometric Functions
Online: Sine, Cosine, Tangent