Parabola
4.0 Focal distance of a point
4.0 Focal distance of a point
From the definition of parabola, $$SP=PM$$
As shown in figure $10$, $$SP = RN{\text{ (because }}PM = RN)$$ $$SP=NV+VR$$
Therefore, Focal distance $$SP = a + {x_1}$$
Similarly, for ${x^2} = 4ay$ type parabola, $$SP = a + {y_1}$$
