PROOF
ABC, (180 – angle A) + (180 – angle B) + (180 – angle C) = 360. We can use addition and subtraction to get angle A + angle B + angle C = 180
PROOF
ABC, (180 – angle A) + (180 – angle B) + (180 – angle C) = 360. We can use addition and subtraction to get angle A + angle B + angle C = 180