Add docs remarks for IsRealNumber handling of infinities

Author: FilipToth

xml/System.Numerics/Complex.xml

@@ -2292,6 +2292,8 @@ A return value of `false` does not imply that <xref:System.Numerics.INumberBase%
 
 This function returns `true` for a complex number `a + bi` where `b` is zero.
 
+This function also returns `true` for <xref:System.Numerics.Infinity> and a complex number `a + bi` where `a` is infinity, but not `b`.
+
           ]]></format>
         </remarks>
         <inheritdoc cref="M:System.Numerics.INumberBase`1.IsRealNumber(`0)" />

xml/System.Numerics/INumberBase`1.xml

@@ -782,6 +782,8 @@ A return value of `false` does not imply that <xref:System.Numerics.INumberBase%
 
 This function returns `true` for a complex number `a + bi` where `b` is zero.
 
+This function also returns `true` for positive and negative infinity.
+
           ]]></format>
         </remarks>
       </Docs>

xml/System.Runtime.InteropServices/NFloat.xml

@@ -2414,6 +2414,8 @@ A return value of `false` does not imply that <xref:System.Numerics.INumberBase%
 
 This function returns `true` for a complex number `a + bi` where `b` is zero.
 
+This function also returns `true` for <xref:System.Runtime.InteropServices.NFloat.PositiveInfinity> and <xref:System.Runtime.InteropServices.NFloat.NegativeInfinity>.
+
           ]]></format>
         </remarks>
         <inheritdoc cref="M:System.Numerics.INumberBase`1.IsRealNumber(`0)" />

xml/System/Double.xml

@@ -3154,6 +3154,8 @@ A return value of `false` does not imply that <xref:System.Numerics.INumberBase%
 
 This function returns `true` for a complex number `a + bi` where `b` is zero.
 
+This function also returns `true` for <xref:System.Double.PositiveInfinity> and <xref:System.Double.NegativeInfinity>.
+
           ]]></format>
         </remarks>
         <inheritdoc cref="M:System.Numerics.INumberBase`1.IsRealNumber(`0)" />

xml/System/Half.xml

@@ -2360,6 +2360,8 @@ A return value of `false` does not imply that <xref:System.Numerics.INumberBase%
 
 This function returns `true` for a complex number `a + bi` where `b` is zero.
 
+This function also returns `true` for <xref:System.Half.PositiveInfinity> and <xref:System.Half.NegativeInfinity>.
+
           ]]></format>
         </remarks>
         <inheritdoc cref="M:System.Numerics.INumberBase`1.IsRealNumber(`0)" />

xml/System/Single.xml

@@ -3171,6 +3171,8 @@ A return value of `false` does not imply that <xref:System.Numerics.INumberBase%
 
 This function returns `true` for a complex number `a + bi` where `b` is zero.
 
+This function also returns `true` for <xref:System.Single.PositiveInfinity> and <xref:System.Single.NegativeInfinity>.
+
           ]]></format>
         </remarks>
         <inheritdoc cref="M:System.Numerics.INumberBase`1.IsRealNumber(`0)" />