Make simple test 1 harder

eureqa.py

@@ -71,7 +71,7 @@ def eureqa(X=None, y=None, threads=4, parsimony=1e-3, alpha=10,
 
     if X is None:
         if test == 'simple1':
-            eval_str = "X[:, 2]**2 + np.cos(X[:, 3]) - 5"
+            eval_str = "X[:, 2]**2 + 5*np.cos(X[:, 3]) - 5"
         elif test == 'simple2':
             eval_str = "np.sign(X[:, 2])*np.abs(X[:, 2])**3.5 + 1/np.abs(X[:, 0])"