Q)  In Fig. AD bisects ∠A, AB = 12 cm, AC = 20 cm and BD = 5 cm, determine CD.

Ans:

∵  AD bisects ∠ A

We know that, according to the angle bisector theorem, the angle bisector of a triangle divides the opposite side into two parts that are proportional to the other two sides of the triangle.

∴ 

∴ 

∴  CD =   = 8.33 cm

Therefore, length of CD is 8.33 cm.