Function to return the length Of diagonal of a parallelogram using sides and angle between them .
static double Length_Diagonal ( int a , int b , double theta ) { double diagonal = Math . Sqrt ( ( Math . Pow ( a , 2 ) + Math . Pow ( b , 2 ) ) - 2 * a * b * Math . Cos ( theta * ( Math . PI / 180 ) ) ) ; return diagonal ; }