how to find the ansers for an elliptic integral.

I am prashanth doing a project using matlab.I am new to matlab.I want to know how to interpret an elliptic integral and how to solve an elliptic integral in matlab. My equation is as follows.

 Input: syms a b phi
        int((1/(sqrt(1-(((2*b)/(a+b))^2)*(sin((pi/4)-(phi/2))^2)))), phi)

Ans:(-2)*ellipticF(pi/4 - phi/2, (4*b^2)/(a + b)^2)

I want to know how the answer has to be interpreted and use in the following steps.

Thanx in advance.

Answer 1

[Walter Roberson]

You need to subs() particular values for "a" and "b" and "phi" into the answer before the value of the elliptic integral can be calculated. For example,

double( subs(Ans, {a, b, phi}, {3, 4, pi/3}) )

[Prashanth Chandrasekar]

Thanx Walter.I want to find out the phi n the equation by iterative process.Can u describe me of the syntax and the applications of different loop conditions.

[Walter Roberson]

EIAns = matlabFunction( subs(Ans, {a, b}, {3, 4}) );   %use appropriate a b
EI_equals = 0.3183;    %whatever you need the integral to come out as if you had the correct phi

rightphi = fzero( @(phi) EIAns(phi) - EI_equals, [0 2*pi]);