Error while performing integration

I am getting error while running this code

 function Q = Zdirection(y)
alpha=30*pi/180;
beta=120*pi/180;
x=1:0.1:5;
z=3;
a=5;
Q1=pi/180*sqrt((a^2-x^2-y.^2).*( ( z*sin(beta).*sin(alpha) - y.*cos(alpha) ).^2+( cos(alpha)*x - cos(beta)*sin(alpha) *z) .^2));
if Q1>=pi/2
    Q1= rem(Q1,pi/2);
end
if Q1<=-pi/2
    Q1= rem(Q1,-pi/2);
end
Q = (Q1); 
 end

 x=1:0.1:5;
a=5;
for i=1:length(x)
z(i)=sqrt(a^2-x(i).^2);
Q2(i)=quad(@Zdirection,0,z(i));
Q2(i)=abs(Q2(i));

end
plot(x,Q2,'Linewidth',2);grid on;shg

I am getting error while running this code

Answer 1

[Alan Stevens]

Like this:

x=1:0.1:5;
a=5;
for i=1:length(x)
z(i)=sqrt(a^2-x(i).^2);
Q2(i)=quad(@(y) Zdirection(y,x(i),a),0,z(i));  %%%%%%%%%%%%%%%
Q2(i)=abs(Q2(i));

end
plot(x,Q2,'Linewidth',2);grid on;shg

 function Q = Zdirection(y,x,a)  %%%%%%%%%%%%%%%%%%%%
alpha=30*pi/180;
beta=120*pi/180;
z=3;
Q1=pi/180*sqrt((a^2-x.^2-y.^2).*( ( z*sin(beta).*sin(alpha) - y.*cos(alpha) ).^2+( cos(alpha)*x - cos(beta)*sin(alpha) *z) .^2));
if Q1>=pi/2
    Q1= rem(Q1,pi/2);
end
if Q1<=-pi/2
    Q1= rem(Q1,-pi/2);
end
Q = (Q1); 
 end

Answer 2

[David Hill]

Or don't even have a Zdirection function

x=1:0.1:5;
a=5;
alpha=30*pi/180;
beta=120*pi/180;
Z=3;
for i=1:length(x)
   z(i)=sqrt(a^2-x(i).^2);
   Q1=quad(@(y)pi/180*sqrt((a^2-x(i)^2-y.^2).*( ( Z*sin(beta).*sin(alpha) - y.*cos(alpha) ).^2...
       +( cos(alpha)*x(i) - cos(beta)*sin(alpha) *Z) .^2)),0,z(i));
   if Q1>=pi/2
      Q1= rem(Q1,pi/2);
   elseif Q1<=-pi/2
      Q1= rem(Q1,-pi/2);
   end
   Q2(i)=abs(Q1);
end
plot(x,Q2,'Linewidth',2);grid on;shg