∠A = BB of line EA – FB of line AB = 180° – 45° – 65° = 70°
∠B = BB of line AB – FB of line BC = 180° – 75° + 45° = 150°
∠C = 360° – FB of line CD + BB of line BC = 75° – 35° = 40°
∠D= 360° – FB of line DE + BB of line CD = 65° + 35° = 100°
Sum of Included Angles = ∠A + ∠B + ∠C + ∠D = 70° + 150° + 40° + 100° = 360°
Check = (2N - 4) X 90° = 360°
Here sum of included angles = check (hence O.K.)
