CSHARP-1402: added $sqrt expression support.

Author: craiggwilson

Docs/reference/content/reference/driver/expressions.md

@@ -622,7 +622,7 @@ p => Math.Log(p.Age, 10);
 p => Math.Log10(p.Age);
 ```
 ```json
-{ $log: ["$Age"] }
+{ $log10: ["$Age"] }
 ```
 
 #### $mod
@@ -652,6 +652,15 @@ p => Math.Pow(p.Age, 10);
 { $pow: ["$Age", 10] }
 ```
 
+#### $sqrt
+
+```csharp
+p => Math.Sqrt(p.Age);
+```
+```json
+{ $sqrt: ["$Age"] }
+```
+
 #### $subtract
 
 ```csharp

src/MongoDB.Driver.Tests/Linq/Translators/AggregateProjectTranslatorTests.cs

@@ -807,6 +807,17 @@ public async Task Should_translate_set_union_reversed()
             result.Value.Result.Should().BeEquivalentTo("it", "icky", "not in here");
         }
 
+        [Test]
+        [RequiresServer(MinimumVersion = "3.1.6")]
+        public async Task Should_translate_sqrt()
+        {
+            var result = await Project(x => new { Result = Math.Sqrt(x.C.E.F) });
+
+            result.Projection.Should().Be("{ Result: { \"$sqrt\": [\"$C.E.F\"] }, _id: 0 }");
+
+            result.Value.Result.Should().BeApproximately(3.31662479, .0001);
+        }
+
         [Test]
         [RequiresServer(MinimumVersion = "3.1.6")]
         public async Task Should_translate_trunc()

src/MongoDB.Driver/Linq/Translators/AggregateLanguageTranslator.cs

@@ -736,6 +736,12 @@ private bool TryTranslateStaticMathMethodCall(MethodCallExpression node, out Bso
                         TranslateValue(node.Arguments[1])
                     });
                     return true;
+                case "Sqrt":
+                    result = new BsonDocument("$sqrt", new BsonArray
+                    {
+                        TranslateValue(node.Arguments[0])
+                    });
+                    return true;
                 case "Truncate":
                     result = new BsonDocument("$trunc", TranslateValue(node.Arguments[0]));
                     return true;