Question

In the given figure, ∆ABC is an obtuse triangle, obtuse-angled at B. If AD⊥CB, prove that AC² = AB² + BC² + 2BC. BD.

Answer 1

Applying Pythagoras theorem in right-angled triangle ADC, we get:

Applying Pythagoras theorem in right-angled triangle ADB, we get:

From equation (1) and (2), we have

This completes the proof.