Answer:
Explanation:
a) Since CD is perpendicular to AB,
∠BDC = ∠CDA = 90°
Comparing ΔABC and ΔACD,
∠BCA = ∠CDA = 90°
∠CAB = ∠DAC (same angle)
since two angle are same in both triangles, the third angles will also be same
∠ABC = ∠ACD
∴ ΔABC and ΔACD are similar
Comparing ΔABC and ΔCBD,
∠BCA = ∠BDC = 90°
∠ABC = ∠CBD(same angle)
since two angle are same in both triangles, the third angles will also be same
∠CAB = ∠DCB
∴ ΔABC and ΔCBD are similar
b) AB = c, AC = a and BC = b
ΔABC and ΔACD are similar

⇒ a² = c*AD - eq(1)
ΔABC and ΔCBD are similar

⇒ b² = c*BD - eq(2)
eq(1) + eq(2):
(a² = c*AD ) + (b² = c*BD)
a² + b² = c*AD + c*BD
a² + b² = c*(AD + BD)
a² + b² = c*(c)
a² + b² = c²