Answer:
Given
- ΔABC with ∠A = 90°
- ΔADC with ∠D = 90°
- The two triangles share same angle ∠C
With two same angles the triangles are similar according to AA similarity postulate:
As we know if triangles are similar then their corresponding sides have same ratio:
- AC/CD = BC/AC ⇒ AC*AC = BC*CD ⇒ AC² = BC*CD
