Answer:
see explanation
Step-by-step explanation:
since BD = DC then Δ BCD is isosceles with base angles being congruent
∠ C = ∠ 2 = [tex]\frac{180-100}{2}[/tex] = [tex]\frac{80}{2}[/tex] = 40°
since ∠ 1 = ∠ 2 then ∠ 1 = 40° , so
∠ B = ∠ 1 + ∠ 2 = 40° + 40° = 80°
the sum of the 3 angles in Δ ABC = 180° , then
∠ A = 180° - ∠ B - ∠ C = 180° - 80° - 40° = 180° - 120° = 60°
then
∠ A = 60° , ∠ B = 80° , ∠ C = 40°
