Trigonometric Ratios in a Circle
This demonstration shows the relationship of the six basic trigonometric ratios to triangles within a unit circle. A unit circle is a circle with a radius of one.
Explore what happens when you select each of the three options. In each case, one of the sides of the triangle is the same length as the radius, and the other two sides are marked with a trigonometric ratio.
Explore what happens when you change the size of the angle. Think about why the secant and cosecant can never be less than one.