Draw an isosceles right triangle of hypotenuse 4 centimetres.
1) Draw a line BC 4 cm.
2) At B, draw ∠XBC = 45°
3) At C, draw ∠YCB = 45°
BX and CY intersect each other at A. and ΔABC is required triangle,
Also,
In ΔABC
∠B = ∠C = 45°
Therefore, AB = AC [i.e. ABC is isosceles]
And By angle sum property of triangle,
∠A + ∠B + ∠C = 180°
⇒ ∠A + 45 + 45 = 180
⇒ ∠A = 90°
Hence, ABC is isosceles.