From Cosine law
float alpha = ( float ) Math . Acos ( ( b2 + c2 - a2 ) / ( 2 * b * c ) ) ; float betta = ( float ) Math . Acos ( ( a2 + c2 - b2 ) / ( 2 * a * c ) ) ; float gamma = ( float ) Math . Acos ( ( a2 + b2 - c2 ) / ( 2 * a * b ) ) ;