Thus, we give a make-graph method of conic section on plane with arbitrary point as foci, arbitrary line as directrices and arbitrary positive number as eccentricity.
For the electrostatic field produced by an uniformly charged spheroid the field strength at an arbitrary point, outside or inside the spheroid, has been deduced by using the superposition principle.
Also, the subject which is a concentrated couple acting on an arbitrary point and in any direction of a plate with four built-in edges, is discussed in this paper.
