Complex: routines to get all square and cubic roots of a complex number

src/Numerics/Complex32.cs

@@ -468,6 +468,29 @@ namespace MathNet.Numerics
             return result;
         }
 
+        /// <summary>
+        /// Evaluate all square roots of this <c>Complex32</c>.
+        /// </summary>
+        public Tuple<Complex32, Complex32> SquareRoots()
+        {
+            var principal = SquareRoot();
+            return new Tuple<Complex32, Complex32>(principal, -principal);
+        }
+
+        /// <summary>
+        /// Evaluate all cubic roots of this <c>Complex32</c>.
+        /// </summary>
+        public Tuple<Complex32, Complex32, Complex32> CubicRoots()
+        {
+            float r = (float)Math.Pow(Magnitude, 1d/3d);
+            float theta = Phase/3;
+            const float shift = (float)Constants.Pi2/3;
+            return new Tuple<Complex32, Complex32, Complex32>(
+                FromPolarCoordinates(r, theta),
+                FromPolarCoordinates(r, theta + shift),
+                FromPolarCoordinates(r, theta - shift));
+        }
+
         /// <summary>
         /// Equality test.
         /// </summary>

src/Numerics/ComplexExtensions.cs

@@ -289,6 +289,29 @@ namespace MathNet.Numerics
             return result;
         }
 
+        /// <summary>
+        /// Evaluate all square roots of this <c>Complex</c>.
+        /// </summary>
+        public static Tuple<Complex, Complex> SquareRoots(this Complex complex)
+        {
+            var principal = SquareRoot(complex);
+            return new Tuple<Complex, Complex>(principal, -principal);
+        }
+
+        /// <summary>
+        /// Evaluate all cubic roots of this <c>Complex</c>.
+        /// </summary>
+        public static Tuple<Complex, Complex, Complex> CubicRoots(this Complex complex)
+        {
+            var r = Math.Pow(complex.Magnitude, 1d/3d);
+            var theta = complex.Phase/3;
+            const double shift = Constants.Pi2/3;
+            return new Tuple<Complex, Complex, Complex>(
+                Complex.FromPolarCoordinates(r, theta),
+                Complex.FromPolarCoordinates(r, theta + shift),
+                Complex.FromPolarCoordinates(r, theta - shift));
+        }
+
         /// <summary>
         /// Gets a value indicating whether the <c>Complex32</c> is zero.
         /// </summary>