Geometrically, the construction goes like this: for any point (cos φ, sin φ) on the unit circle, draw the line passing through it and the point . This point crosses the -axis at some point . One can show using simple geometry that . The equation for the drawn line is . The equation for the intersection of the line and circle is then a quadratic equation involving . The two solutions to this equation are and . This allows us to write the latter as rational functions of (solutions are given below).