From Cosine law
alpha = math . acos ( ( b2 + c2 - a2 ) / ( 2 * b * c ) ) ; NEW_LINE betta = math . acos ( ( a2 + c2 - b2 ) / ( 2 * a * c ) ) ; NEW_LINE gamma = math . acos ( ( a2 + b2 - c2 ) / ( 2 * a * b ) ) ; NEW_LINE