How do I solve this sigma_tt in numerical analysis

%% sv=95; sh=50; sH=50; Pp=49; v=0.15; inc=0 theta=linspace(0,360,40); az=0; r=0:0.1:3.98; % wellbore itself) sx = sH.*(cos(az).* cos(r)).^2 + sh.*(sin(az).*cos(r)).^2 + sv.*(-sin(r).^2);

sy = sH.*(-sin(az)).^2 + sh.*(cos(az).^2);

sz = sH.*((cos(az).* sin(r)).^2) + sh.*(sin(az).^2).*(sin(r).^2)+ sv.*(cos(r).^2);

sxy =(sH.*cos(az).* cos(r).*-sin(az))+ (sh.*sin(az).*cos(r).*cos(az))+(sv.*-sin(r).*0);

syz = (sH.*-sin(az).*sin(r).*cos(az))+(sh.*cos(az).* sin(r).*sin(az))+(sv.*cos(r).*0);

sxz = (sH.*cos(az).* cos(az).*sin(r).*sin(r))+(sh.*sin(az).*cos(r).*sin(az).*sin(r))+(sv.*-sin(r).*cos(r));

sigma_tt = 0.5.*(sx + sy).*(1 + 1) - 0.5.*(sx - sy).*(1 + 3.*1).*cos(2.*theta) - sxy.*(1 + 3.*1).*sin(2.*theta);