≈c = 90 ac⊥af

∴△ABC and△△△ APQ are right triangles.

HL theorem can be used to prove the congruence of two right triangles.

PQ = AB

Point p has moved for 2.5 seconds, that is, CP=5cm.

AC = 8cm，BC=3cm。

∴AP=BC=3cm

∴△ABC≌△APQ(HL)。