This applet demonstrates how the tangent ratio of an angle is also the length of a line segment - specifically, a line segment that is tangent to the unit circle. To see this segment, click "Click here to see tangent line info". The tangent segment will be the purple one called DF, which has one endpoint at the point of tangency, and the other on the x-axis.[br][br]Use the slider to change the angle, and watch how the tangent ratio (in absolute value) and the length of the segment DF are always the equal to each other, regardless of the angle. [br][br]To see why that is, click the other check boxes in sequence.