Special Triangles

How to find the trigonometric values of some special angles without using a calculator to approximate them.

  1.  \rhd Trig values of special angles (7:53)
    Sal finds the trig values of \frac{\pi}{4} on the unit circle using triangles.
  2.  \star Trig values of special angles
    Students are asked to find the trig values of angles such as -\frac{2\pi}{3} without using a calculator.