1. A development is a
flat representation or pattern that when folded together creates a 3-D object.
OR
A development is
the unfold/unrolled flat/plane figure of a 3-D object. Called also a pattern, the plane may show the true size of each
area of the object. When the pattern is cut, it can be rolled or folded back
into the original object.
2. (a) Parallel-line
development
(b) Radial-line
development
(c) Triangulation development
a) Parallel-line Method: It is used for developing prisms and single
curved surfaces like cylinders, in which all the edges/generation of lateral
surfaces are parallel in each other.
b) Radial-line
Method: It is employed for
pyramids and single curved surfaces like cones in which the apex is taken as
centre and the slant edge or generator as radius of its development.
c) Triangulation Method: It is used for developing transition
pieces.
NB:
There is other type of development that is called
Approximate Method
Approximate Method: It is employed for double curved
surfaces like spheres, as they are theoretically not possible to develop. The
surface of the sphere is developed by approximate method. When the surface is
cut by a series of cutting planes, the cut surfaces is called a zone.
3.
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