Intersection between the two curves

t = linspace(0, 1500, 250);                                             % Independent Variable
f1 = 100*sin(2*pi*t/100);                                               % First Curve
f2 = 10*sin(2*pi*t/100) - t*0.2;                                        % Second Curve
zci = @(v) find(v(:).*circshift(v(:), [-1 0]) <= 0);                    % Returns Approximate Zero-Crossing Indices Of Argument Vector
df = f1 - f2;
fzx = zci(df);
for k = 2:numel(fzx)-1                                                  % Interpolation Loop (Do Not Include First Or Last Values)
    ixr = [fzx(k)-1 fzx(k)+1];                                          % Interpolation Index Range
    tv = t(ixr);
    dv = df(ixr);    
    B = [tv(:) [1; 1]] \ dv(:);                                         % Estimate Parameters
    ti(k) = -B(2) / B(1);                                               % ‘t’ At Zero-Crossing
    f1v(k) = interp1(tv, f1(ixr), ti(k));                               % ‘f1’ At Intersection
    f2v(k) = interp1(tv, f2(ixr), ti(k));                               % ‘f2’ At Intersection
end
figure
plot(t, f1,    t, f2)                                                   % Plot Curves
hold on
plot(ti, f1v, 'x',    ti, f2v, '+')                                     % Plot Intersections
hold off
grid