Answer 1

In the given ΔABC, ∠A= 100°, AD bisects  ∠Aand AD ⊥ BC.

Here, we need to find ∠B.

As, AD bisects∠A,

We get, 

∠BAD = ∠DAC

100 = 2∠BAD

∠BAD = 50°

Now, according to angle sum property of the triangle

In ΔABD

∠A + ∠B + ∠D = 180°

   50° + ∠B + 90° = 180°

         140° + ∠B = 180°

                   ∠B = 180° - 140°

                         = 40°

Hence, ∠B = 40°