## Definitions, examples, counter examples of similar triangles.

A, B and C are three identical bulbs, which of the following change occurs in the brightness of bulb, when switch S is closed

(a) A remains same, then B decreases

(b) A increases then B decreases

(c) A increases then B remains same

(d) A decreases then B increases

## Definitions, examples, counter examples of similar triangles.

5.1    INTRODUCTION
In previous classes, we have learnt about the congruency of two geometric figures. In this chapter we shall learn about these geometric figures. Which have the same shape but not necessary have the same size. These kind of geometric figures are known as similar figures. So the congruent figures are always similar figures but similar figures need not be congruent figures.

(i)    Two line segments are similar

(The two line segments are congruent if they have the same length)

(ii)    Two circles are similar.
(The two circles are congruent. If they have the same radius)

5.2    similar Polygons
Two polygons of the same number of sides are said to be similar. If
(i)    Their corresponding angles are equal
(ii)    Their corresponding sides are in the same ratio