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Integral problem in Matlab

  1. Jul 2, 2012 #1
    I want to find the definite integral of

    arccos(sqrt(1+x)/10)/(sqrt(x)*x^(2/3))​

    ,over [0,pi/2].

    I ran the following code in Matlab,

    "syms w

    double(vpa(int(acos((w + 1)^(1/2)/10)/(w^(1/2)*(w + 1)^(3/2)),w,0,pi/2)))"

    and got this error message,

    "??? Error using ==> mupadmex
    Error in MuPAD command: DOUBLE cannot convert the input expression into a
    double array.

    If the input expression contains a symbolic variable, use the VPA function
    instead.

    Error in ==> sym.sym>sym.double at 936
    Xstr = mupadmex('symobj::double', S.s, 0);

    Error in ==> HW at 4
    double(vpa(int(acos((w + 1)^(1/2)/10)/(w^(1/2)*(w + 1)^(3/2)),w,0,pi/2)))".

    Anybody has met such situation like me before? I appreciate any comment!
     
  2. jcsd
  3. Jul 2, 2012 #2
    Hello there! I think that int() cannot be used here, since the integral will need to be evaluated numerically. Try using quadl() instead:

    Code (Text):
    this = @(w)acos((w+1).^(1/2)/10)./(w.^(1/2).*(w+1).^(3/2)); % note the elementwise operations (.^, ./, .*)

    quadl(this,0,pi/2)
    Hopefully that helps!
     
  4. Jul 2, 2012 #3
    Thanks a lot! It exactly settles the issue.
     
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