Asked by Tarang
on 24 May 2013

I have a function in 3 variables in "B y t" which I want to integrate wrt 'y' only. I used int function but it is showing Explicit integral cannot be found. I tried numerical integration also giving limits from (0 to b/2) but same error is there. The code is mentioned below

syms B y t; C_d=0.1; w=2; density=1.225; U=3.2; a=0.005; b=0.05; R=10; c=2*a*((1-(y/b)^2)^0.5); C1= 0.5*R/(2.32+R); C2=0.181+(0.722/R); A0=0.0348; theta=-B*y*sin(w*t); thetarate=-B*y*w*cos(w*t); thetarate2=-B*y*(w^2)*sin(w*t); thetabar=sin(w*t)*B*b/4; h=-0.0785*cos(w*t); h_dash=0.0785*w*sin(w*t); A=0.049*(sin(2*t))*cos(B*y*sin(2*t))+0.00234*((1-400*(y^2))^0.5)*B*y*cos(2*t)-B*(y*sin(2*t)-0.0125*sin(2*t)); C=(117*B*cos(2*t)*(1 - 400*y^2)^(1/2))/50000 - (49*B*sin(2*t)^2*sin(B*y*sin(2*t)))/1000 - B*sin(2*t) - (117*B*y^2*cos(2*t))/(125*(1 - 400*y^2)^(1/2)); k=(c*w)/(2*U); F=1-((C1*(k^2))/((k^2)+(C2^2))); G=-(C1*C2*k)/((k^2)+(C2^2)); w0=U*2*(A0+thetabar)/(2+R); alphadash=(R/(2+R))*(F*A+((c/2*U)*G*C))-(w0/U); Cn=2*pi*(alphadash+A0+thetabar); V=((U*cos(theta)-0.0785*w*sin(w*t)*sin(theta))^2)+(U*(alphadash+theta)-(0.5*c*thetarate))^0.5; v_dash=(U*C)-(0.25*c*thetarate2); N_a=0.25*pi*c^2*density*v_dash; N_c=0.5*density*U*V*Cn*c; N=N_a+N_c; J=2*pi*(alphadash+thetabar-(0.25*c*thetarate/U))^2*density*U*V*c/2; V_x=U*cos(theta)-(h_dash)*sin(theta); K=-2*pi*A0*(alphadash+thetabar)*density*U*V*c/2; L=C_d*density*(V_x)^2*c/2; M=J-K-L; O=N*cos(theta)+M*sin(theta); %final function to integrate P=M*cos(theta)-N*sin(theta); %final function to integrate X=int(O); Y=int(P);

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## 2 Comments

## Walter Roberson (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/76858#comment_150802

Please show the content of "O" and "P" . It could well be that they just do not have an explicit integral.

Please show your attempt to do numeric integration. Is the message exactly the same?

## Tarang (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/76858#comment_150929

O and P are very big function in y t and B. When I gave the command... int (O, y, 0, b/2) after 3hrs it said explicit integration can't be found.. and wrote.......... int (O, y=0..0.025).

I think the function is non integrable. But then it should have given the numerical integral. Can I just know how can I integrate above using simpson rule? Should I use linspace and loops or is there any other function for this? Thanks