This value of 0 is the same for all parabolas which pass through D and E and have their axes at right angles to KL.
As the loads move over the girder, the points C, D, E describe the parabolas M1, M2, M3 i the middle ordinates of which are 4W 1 1, 4W 2 1, and 4W3l.
The three lightly W2 dotted parabolas are the curves of maximum moment for each of the loads taken separately.
In the geometry of plane curves, the term parabola is often used to denote the curves given by the general equation a' n x n = ym+n, thus ax= y 2 is the quadratic or Apollonian parabola; a 2 x = y 3 is the cubic parabola, a 3 x = y4 is the biquadratic parabola; semi parabolas have the general equation ax n-1 = yn, thus ax e = y 3 is the semicubical parabola and ax 3 = y 4 the semibiquadratic parabola.
Diverging parabolas are cubic curves given by the equation y 2 = 3 -f-bx 2 -cx+d.