diff --git a/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs b/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
index 43fce93..e6fdb4a 100644
--- a/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
+++ b/ClosedXML/Excel/CalcEngine/Functions/MathTrig.cs
@@ -28,6 +28,7 @@
             ce.RegisterFunction("COS", 1, Cos);
             ce.RegisterFunction("COSH", 1, Cosh);
             ce.RegisterFunction("COT", 1, Cot);
+            ce.RegisterFunction("COTH", 1, Coth);
             ce.RegisterFunction("CSCH", 1, Csch);
             ce.RegisterFunction("DECIMAL", 2, MathTrig.Decimal);
             ce.RegisterFunction("DEGREES", 1, Degrees);
@@ -131,6 +132,15 @@
             return 1 / tan;
         }
 
+        private static object Coth(List<Expression> p)
+        {
+            double input = p[0];
+            if (input == 0)
+                throw new DivisionByZeroException();
+
+            return 1 / Math.Tanh(input);
+        }
+
         private static object Csch(List<Expression> p)
         {
             if (Math.Abs((double)p[0].Evaluate()) < Double.Epsilon)
diff --git a/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs b/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
index 8c95b10..06ac520 100644
--- a/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
+++ b/ClosedXML_Tests/Excel/CalcEngine/MathTrigTests.cs
@@ -79,6 +79,38 @@
             Assert.Throws<DivisionByZeroException>(() => XLWorkbook.EvaluateExpr("COT(0)"));
         }
 
+        [TestCase(-10, -1.000000004)]
+        [TestCase(-9, -1.00000003)]
+        [TestCase(-8, -1.000000225)]
+        [TestCase(-7, -1.000001663)]
+        [TestCase(-6, -1.000012289)]
+        [TestCase(-5, -1.000090804)]
+        [TestCase(-4, -1.00067115)]
+        [TestCase(-3, -1.004969823)]
+        [TestCase(-2, -1.037314721)]
+        [TestCase(-1, -1.313035285)]
+        [TestCase(1, 1.313035285)]
+        [TestCase(2, 1.037314721)]
+        [TestCase(3, 1.004969823)]
+        [TestCase(4, 1.00067115)]
+        [TestCase(5, 1.000090804)]
+        [TestCase(6, 1.000012289)]
+        [TestCase(7, 1.000001663)]
+        [TestCase(8, 1.000000225)]
+        [TestCase(9, 1.00000003)]
+        [TestCase(10, 1.000000004)]
+        public void Coth_Examples(double input, double expected)
+        {
+            var actual = (double)XLWorkbook.EvaluateExpr(string.Format(@"COTH({0})", input.ToString(CultureInfo.InvariantCulture)));
+            Assert.AreEqual(expected, actual, tolerance * 10.0);
+        }
+
+        [Test]
+        public void Cot_On0_ThrowsDivisionByZeroException()
+        {
+            Assert.Throws<DivisionByZeroException>(() => XLWorkbook.EvaluateExpr(@"COTH(0)"));
+        }
+
         [TestCase("FF", 16, 255)]
         [TestCase("111", 2, 7)]
         [TestCase("zap", 36, 45745)]