Big Ideas:
The unit circle has a radius of 1, so sin (t) =y/1=y and cos(t) =x/1=x and any point on the unit circle (x, y) can be labeled (cos(t),sin(t)). Therefore, cos(t) and sin(t) can be evaluated using the reference triangles derived from Pythagorean Theorem.
After an investigation to review the standard 30-60-90 and 45-45-90 triangles that were used in geometry, students can apply similar triangles to the unit circle to create a table of "Special Angles." These Special Angles will help students to make meaning of the functions sine, cosine, and tangent.
Vocabulary: Special Angles
Lesson plan