Question: What is an Enlargement ?


An enlargement is a transformation which changes the size of an object without changing its shape, rather as a projector enlarges the details of a photographic slide onto a screen.

An enlargement of a diagram can be constructed by first drawing lines from a point O, the center of enlargement, through points of the figure such as A, B and C, then marking off the image points A1 B1 C1 so that OA1 = kOA, OB1 = kOB where k is the scale factor of the enlargement. In the example shown, triangle ABC has been enlarged with scale factor k = 2. (k is sometimes known as the linear scale factor).

The center of the enlargement may be a point outside the object, inside it, or on its boundary. Also the scale factor can be negative. In this case it is still true that for every point P its image point P1 is given by OP1 = kOP.