Prove that an altitude divides an equilateral triangle into two congruent triangles.

Measure and state which of the line segments are congruent?

If $∆\mathrm{PQR}\cong ∆\mathrm{XYZ}$, then $\angle \mathrm{X}=$?

What is the length of side $\mathrm{QR}$, if the two triangles are congruent.

Which of the following criterion can be used for proving $∆\mathrm{ABC}$ and $∆\mathrm{DEF}$ congruent?

In the adjoining figure, $∆\mathrm{ADC}\cong ∆\mathrm{ABC}$, which of the following is not true?

For the adjoining figure, write the correct correspondence for the congruency of the given two triangles.