Question

In ΔABC, ∠B = 90°, find ∠A if BC is equal to AВ.

Answer 1

Given: In triangle ABC, ∠B = 90° and BC = AB.

Step-wise calculation:

1. BC = AB ⇒ triangle ABC is isosceles with the equal sides at B, so ∠A = ∠C.

2. Sum of angles in a triangle:

∠A + ∠B + ∠C = 180°.

With ∠B = 90°, we get ∠A + ∠C = 90°.

3. From (1) ∠A = ∠C. 

So, 2∠A = 90° 

⇒ ∠A = `90^circ/2`

⇒ ∠A = 45°