Question

how to find similarly of triangles?

Answer 1

Two triangles are Similar if the only difference is size (and possibly the need to turn or flip one around).

These triangles are all similar:

triangles similar different sizes and rotations

(Equal angles have been marked with the same number of arcs)

Some of them have different sizes and some of them have been turned or flipped.



For similar triangles:

corresponding angles on two triangles
All corresponding angles are equal

and

corresponding sides on two triangles
All corresponding sides have the same ratio
Also notice that the corresponding sides face the corresponding angles. For example the sides that face the angles with two arcs are corresponding.

Corresponding Sides
In similar triangles, corresponding sides are always in the same ratio.

For example:

triangles similar R: (6,7,8) and S: (b,a,6.4)

Triangles R and S are similar. The equal angles are marked with the same numbers of arcs.