Revert breaking change

src/Numerics/Integrate.cs

@@ -46,11 +46,23 @@ namespace MathNet.Numerics
         /// <param name="intervalEnd">Where the interval stops, inclusive and finite.</param>
         /// <param name="targetAbsoluteError">The expected relative accuracy of the approximation.</param>
         /// <returns>Approximation of the finite integral in the given interval.</returns>
-        public static double OnClosedInterval(Func<double, double> f, double intervalBegin, double intervalEnd, double targetAbsoluteError = 1E-8)
+        public static double OnClosedInterval(Func<double, double> f, double intervalBegin, double intervalEnd, double targetAbsoluteError)
         {
             return DoubleExponentialTransformation.Integrate(f, intervalBegin, intervalEnd, targetAbsoluteError);
         }
 
+        /// <summary>
+        /// Approximation of the definite integral of an analytic smooth function on a closed interval.
+        /// </summary>
+        /// <param name="f">The analytic smooth function to integrate.</param>
+        /// <param name="intervalBegin">Where the interval starts, inclusive and finite.</param>
+        /// <param name="intervalEnd">Where the interval stops, inclusive and finite.</param>
+        /// <returns>Approximation of the finite integral in the given interval.</returns>
+        public static double OnClosedInterval(Func<double, double> f, double intervalBegin, double intervalEnd)
+        {
+            return DoubleExponentialTransformation.Integrate(f, intervalBegin, intervalEnd, 1e-8);
+        }
+
         /// <summary>
         /// Approximates a 2-dimensional definite integral using an Nth order Gauss-Legendre rule over the rectangle [a,b] x [c,d].
         /// </summary>