**31) Define Hyperbola ?**

It is a curve which is generated by point moving so that the differences of the distances from any point of the curve to two fixed points(foci),is a constant equal to the transverse axis of the hyperbola.

**32) What is an involute ?**

Involute is a spiral curve made by a point on a perfectly taut string as it unwinds from around a shape such as a circle or polygon.

**33) Define a Cycloid ?**

It is a curve which is generated by a point in the plane of a circle that rolls along a straight line.

**34) What is a Helix ?**

It is a curve which is generated by a point moving at uniform rate around and advancing parallel to, or at varying distances from an axis.

**35) What is meant by projection of an object ?**

Representation of an object on paper is called projection of an object.

**36) What do you mean by projectors ?**

Projectors are the imaginary lines drawn from the object to the plane.

**37) What is the plane of projection ?**

It is the plane on which the projection of the object is taken.

**38) Explain the principle of orthographic projection ?**

It is the method of representing the exact shape of an object in two or more views on planes. In this projection all the projectors are parallel to each other and perpendicular to the plane of projection. Projectors are assumed to come from infinity. It is generally used in machine drawing.

**39) What are the principle views of an orthographic projection ?**

(a)Front view or Elevation(b)Top view or Plan (c)Side view

**40) Which orthographic projection has been recommended by Bureau of Indian Standard(BIS) ?**

Third angle projection

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