46 MATHEMATICAL FORMULA AND ELLIPTIC FUNCTIONS 



I 



2.404 Length of arc of parabola measured from vertex, 



s = x(x + a) + a log i + + 



Area OPMO = - xy. 

 2.405 Polar equation of parabola: 



= angle XFP, 



20, 



I - COS 



n 

 U 



2.406 Equation of Parabola in terms of p, the perpendicular from F upon the 

 tangent, and r, the radius vector FP: 



I = semi latus rectum. 



2.410 Ellipse (Fig. 4). 



FIG. 4 

 2.411 O, Centre; F, F', Foci. 



Equation of Ellipse origin at O: 



x 2 y 2 

 a 2 b 2 



x = OM, y = MP, a = 



= OB. 



