STEP 3:
Hand in the third worksheet:
Combine the coordinates of the plotted points and the angles on the graph. Tell them that:
- Each point has two coordinates: abscissa and ordinate;
- To each point, the abscissa is the value of a cosine and the ordinate the value of a sine of a related angle (or arc, since every angle has vertex on the center of a unit circle);
- Pick some angle by way of example like: 90° (or p/2 rad) is related to the point (0, 1) so, cosine of 90° is equals to zero and sine of 90° is equals to one;
- Invite the students to write down a table with the values of cosines and sines of the angles 0°, 90°, 180°, 270° and 360°;
- Begin the concept of trigonometric "cycle" instead of just "circle" showing them that we can obtain an infinite number of angles greater than 360°;
- Depending on the learning ability of the class, introduce also the concept of negative angles.
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