You may even remember from high school that the radius is any straight line that starts from the center of the circle and ends at its perimeter. A unit circle is just a circle that has a radius ...

Part of that is the way it's taught. Students are taught the "unit circle" and its relationship to trigonometry, but many fail to make the leap on how crucial circles are for trig functions.

This branch of math, known as trigonometry, has everyday practical applications such as construction, GPS, plumbing, video games, engineering, carpenter work and air flight navigation. To memorize a ...