Unit Circle: is basically a circle that has a center point located at point (0,0) and has a radius of 1.
What is the circumference of the unit circle?
Circumference of a circle of radius ‘r’ is 2πr.
trigon: Greek for ‘triangle’.
metry (metric?): Greek for ‘measure’.
terminal point: The terminal point on the unit circle determined by the real number t.
To further explain terminal point, imagine that you’re standing on top of point (1,0) on the unit circle (the far right of the circle). Then you walk whatever distance until you heart desires, let’s just say you stop at Quadrant 2… That point that you stopped on, is the terminal point. You can even go past the the initial point of (1,0), but you’d still get the same distance if you did a full period and ended on the same spot as well.
reference number of a number t: The reference number of t, known as tref, is the shortest distance along the unit circle from the terminal point ’t’ back to the ‘x-axis’.
π ≈ 3.14;
2π ≈ 6.28;
equation of the unit circle: x2 + y2 = 1