Trigonometric Ratios in a Circle
- Dr. John Brungardt
The following diagram shows how the various trigonometric ratios are related to each other in a functional way. Click and drag point D to see these relationships.
The construction also shows how the names of the trigonometric ratios originated, from the names of the lines in the diagram. Note how the values of the ratios are equal to the lengths of the lines, if the radius is thought of as equal to 1.