www.pudn.com > matlab±à³Ì.zip > calc_roots.m, change:1997-12-28,size:2129b

%  Script file: calc_roots.m 
% 
%  Purpose:  
%    This program solves for the roots of a quadratic equation  
%    of the form a*x**2 + b*x + c = 0.  It calculates the answers 
%    regardless of the type of roots that the equation possesses. 
% 
%  Record of revisions: 
%      Date       Programmer          Description of change 
%      ====       ==========          ===================== 
%    12/04/97    S. J. Chapman        Original code  
% 
% Define variables: 
%   a            -- Coefficient of x^2 term of equation 
%   b            -- Coefficient of x term of equation 
%   c            -- Constant term of equation 
%   discriminant -- Discriminant of the equation 
%   imag_part    -- Imag part of equation (for complex roots) 
%   real_part    -- Real part of equation (for complex roots) 
%   x1           -- First solution of equation (for real roots) 
%   x2           -- Second solution of equation (for real roots) 
 
% Prompt the user for the coefficients of the equation 
disp ('This program solves for the roots of a quadratic '); 
disp ('equation of the form A*X^2 + B*X + C = 0. '); 
a = input ('Enter the coefficient A: '); 
b = input ('Enter the coefficient B: '); 
c = input ('Enter the coefficient C: '); 
 
% Calculate discriminant 
discriminant = b^2 - 4 * a * c; 
 
% Solve for the roots, depending on the value of the discriminant 
if discriminant > 0 % there are two real roots, so... 
 
   x1 = ( -b + sqrt(discriminant) ) / ( 2 * a ); 
   x2 = ( -b - sqrt(discriminant) ) / ( 2 * a ); 
   disp ('This equation has two real roots:'); 
   fprintf ('x1 = %f\n', x1); 
   fprintf ('x2 = %f\n', x2); 
 
elseif discriminant == 0  % there is one repeated root, so... 
 
   x1 = ( -b ) / ( 2 * a ); 
   disp ('This equation has two identical real roots:'); 
   fprintf ('x1 = x2 = %f\n', x1); 
 
else % there are complex roots, so ... 
 
   real_part = ( -b ) / ( 2 * a ); 
   imag_part = sqrt ( abs ( discriminant ) ) / ( 2 * a ); 
   disp ('This equation has complex roots:'); 
   fprintf('x1 = %f +i %f\n', real_part, imag_part ); 
   fprintf('x1 = %f -i %f\n', real_part, imag_part ); 
 
end