Answer:
∠ A = 18.2°
Step-by-step explanation:
The sum of the 3 angles in a triangle is 180° , that is
∠ A + ∠ B + ∠ C = 180°
given ∠ B = 143.6° and
Given that ∠ A and ∠ C are congruent (equal ) , then ∠ C = ∠ A , so
substitute ∠ C = ∠ A in the equation
∠ A + 143.6° + ∠ A = 180°
2 ∠ A + 143.6° = 180° ( subtract 143.6° from both sides )
2 ∠ A = 36.4° ( divide both sides by 2 )
∠ A = 18.2°
