--- a
+++ b/Cobiveco/functions/secant.m
@@ -0,0 +1,42 @@
+function [x,flag,iter] = secant(fun, x1, x2, tol, maxit)
+
+if nargin < 5
+    maxit = 100;
+end
+
+f1 = fun(x1);
+if abs(f1) < tol
+    x = x1;
+    return;
+end
+
+f2 = fun(x2);
+if abs(f2) < tol
+    x = x2;
+    return;
+end
+
+flag = 1;
+
+for iter = 1:maxit
+    if abs(f1-f2) < 1e-12
+        flag = 0;
+        break;
+    end
+    x = x1 - (x1-x2)/(f1-f2) * f1;
+    f = fun(x);
+    
+    fprintf('%d\t%.3e\t%.3e\n', iter, x, abs(f));
+    
+    if abs(f) < tol
+        flag = 0;
+        break;
+    else
+        x2 = x1;
+        f2 = f1;
+        x1 = x;
+        f1 = f;
+    end
+end
+
+end
\ No newline at end of file