Answer
DB =$\sqrt 52$
Work Step by Step
Consider the triangle ABC is a right angled triangle
According to the Pythagoras theorem $(AC)^{2}=(AB)^{2}+(BC)^{2}$ .......(1)
Given AC = 5, BC = 3, DA = 6
Substitute these values in equation (1) we get
$(5)^{2}=(AB)^{2}+(3)^{2}$
$(AB)^{2}$ = 25 -9
$AB = \sqrt 16$
$AB = 4 cm$
From the figure Consider DAB is a right angled triangle
According to the Pythagoras theorem $(DB)^{2}=(DA)^{2}+(AB)^{2}$ .......(2)
Substitute DA and AB values in equation (2) we get
$(DB)^{2}=(6)^{2}+(4)^{2}$
$(DB)^{2}= 36+16$
$DB = \sqrt 52$