How do I find and display the intersection of my functions?

Hi guys,

I want to find the intersection of y3 and y4,

   x=(0:0.5:80).';
y1=(0.02049/0.4)*x;
y2=(0.53*60./(1+(1.331./(sqrt(0.0631*x./(83.18-x))).^3)));
y3=(0.53*60./(1+(1.331./(sqrt(0.0631*x./(83.18-x))).^3)))-(0.02049/0.4)*x;
y4=(0.02049/0.4)*x-(0.53*60./(1+(1.331./(sqrt(0.0631*x./(83.18-x))).^3)));
figure
plot(x,y1,'r')
hold on 
plot(x,y2,'c')
plot(x,y3,'g')
plot(x,y4,'b')
legend('Line1','Line2','Line3','Line4')
axis([0 80 -1 3.5])

i tried to use

   C = intersect(y3,y4)

I get C = 0, but I want the intersection near x = 70;

Answer 1

[Star Strider]

Try this:

x = linspace(0, 80, 200);
y3 = @(x) (0.53*60./(1+(1.331./(sqrt(0.0631*x./(83.18-x))).^3)))-(0.02049/0.4)*x;
y4 = @(x) (0.02049/0.4)*x-(0.53*60./(1+(1.331./(sqrt(0.0631*x./(83.18-x))).^3)));
y34 = @(x) y3(x) - y4(x);                           % Subtract Functions
x0 = 40;
xi = fzero(y34, x0);

figure(1)
plot(x, y3(x),  x, y4(x))
hold on
plot(xi, y3(xi), 'pr')
hold off
grid

xi =
    68.8010