random number estimate value

Hi

In this problem I know that for a=0.5 q=125. I try fo find that now I don't know a value but I know q. How can I estimate a value and use random command for a value.

a =rand(); % estimate number

b = 0.1;

fun = @(x,y) a*x.^2 + b*y.^2;

q = integral2(fun,0,5,-5,0) % real value 125

Answer 1

[Star Strider]

Try this:

b = 0.1;
fun = @(x,y,a,b) a*x.^2 + b*y.^2;
q_fcn = @(a) integral2(@(x,y)fun(x,y,a,b),0,5,-5,0) % real value 125
a = fzero(@(a)q_fcn(a) - 125, 1)

producing:

a =
          0.5

This solves for ‘a’ given ‘b’, ‘q’ and the limits of integration.

Answer 2

[erhan aksu]

Thanks Star Strider

[Star Strider]

As always, my pleasure.