112 MATHEMATICS
FD ✆ AB, DE ✆ BC and EF ✆ CA
and F ✆ A, D ✆ B and E ✆ C
So, ✂FDE ☎✂ABC but writing ✂DEF ☎✂ABC is not correct.
Give the correspondence between the triangle in Fig. 7.4 (iv) and ✂ABC.
So, it is necessary to write the correspondence of vertices correctly for writing of
congruence of triangles in symbolic form.
Note that in congruent triangles corresponding parts are equal and we write
in short ‘CPCT’ for corresponding parts of congruent triangles.
7.3 Criteria for Congruence of Triangles
In earlier classes, you have learnt four criteria for congruence of triangles. Let us
recall them.
Draw two triangles with one side 3 cm. Are these triangles congruent? Observe
that they are not congruent (see Fig. 7.5).
Fig. 7.5
Now, draw two triangles with one side 4 cm and one angle 50° (see Fig. 7.6). Are
they congruent?
Fig. 7.6