Rand Barnett - Make a 3d video gaming engine with basic math and programming - Part 2 Trigonometry
The main thing we do in trigonometry is find the x/y coordinates of points along a circle. Here is a interactive animation of it:
Move your mouse over the black circle. The blue line (the point where the blue and red lines touch) is the y coordinate (latitude on a map). The yellow line (the point where the yellow and blue touch) is the x coordinate (longitude on a map). For any point around the circle, there is an x and y coordinate. It also forms a triangle.