The whole mechanism given here is a slider crank mechanism. The asked point C which is at end of crank always rotates around D and member length will not change so curve traced by that point is circle.

Reference line will be xy line which is formed by intersection of vertical plane and horizontal plane. In first angle projection projections of object is taken by placing object in 1st quadrant and top view is projected on to horizontal plane which is after reference line.

The two points given are foci of ellipse. Ellipse is a curve whose eccentricity is less than one. The process given is one of methods to draw an ellipse in an easy way. Since sum of distances from two fixed points to point P on curve is always constant.

It is a curve traced out by a point moving in such a way that it?s movement towards or away from pole is uniform with increase of vectorial angle from starting line. These types of curves are used in drawing profiles of cam.

Orthographic projection is representation of two or more views on mutual perpendicular projection planes. But for oblique projection, object is viewed in only one view. And in isometric view object is kept resting on ground on one of its corners with a solid diagonal perpendicular to V.P.

The line formed by an intersection of principal planes or reference planes of projection that is vertical plane or frontal plane and horizontal plane is called reference line which is denoted by letters xy.

If object is placed in 1st quadrant and object?s surface is coinciding with both horizontal plane and vertical plane which indirectly saying distance from both planes is zero so both top and front views of that object touches reference line.

There is no or chance of locating point P whose distance from a fixed line is constant or than a line parallel to given line and passing through point P and this help in drawing parallel lines.

As object is in first quadrant and front view projects on vertical plane and top view projects on horizontal plane. And for representing projection horizontal plane has to turn 90 degrees in clockwise direction. The top view will be below front view.

As object is in third quadrant and front view projects on a vertical plane and top view projects on horizontal plane. And for representing projection horizontal plane has to turn 90 degrees in clockwise direction.