From the given construction of a triangle ABC with side BC = 7 cm, ∠B = 45°, and ∠C = 30°. find the value of angle A.

Given, ∠B = 45°, and ∠C = 30°

In ∆ABC, ∠A + ∠B + ∠C = 180° … [angle sum property of a triangle]
=> ∠A + 45° + 30° = 180°

=> ∠A + 75°  = 180°
=> ∠A = 180° – 75^o = 105°

Thus, ∠A = 105°