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!