Given: ABC is a right-angled triangle with ∠A = 90°, and a perpendicular AD is drawn from the right angle vertex A to the hypotenuse BC. To Prove: Triangles ∆DBA and ∆DAC are similar to each other. Proof: In ∆DBA and ∆ABC: ∠BDA = ∠BAC = 90° And ∠ABD = ∠CBA Therefore, the remaining angle ∠BAD = ∠BCA So, ∆DBA and ∆ABC are equiangular Therefore, ∆DBA is similar to ∆ABC Similarly, in ∆DAC and ∆ABC: ∠ADC = ∠BAC = 90° ∠ACD = ∠BCA Therefore, the remaining angle ∠CAD = ∠CBA So, ∆DAC and ∆ABC are equiangular Therefore, ∆DAC is similar to ∆ABC Now, since both ∆DBA and ∆DAC are similar to ∆ABC, Therefore, ∆DBA is similar to ∆DAC (Proved)