Math.Sqrt(Double) 方法

定義

傳回指定數字的平方根。Returns the square root of a specified number.

public:
 static double Sqrt(double d);
public static double Sqrt (double d);
static member Sqrt : double -> double
Public Shared Function Sqrt (d As Double) As Double

參數

d
Double

要找出其平方根的數字。The number whose square root is to be found.

傳回

下表的其中一個值。One of the values in the following table.

d 參數d parameter 傳回值Return value
零或正數Zero or positive d 的正平方根。The positive square root of d.
Negative NaN
等於 NaNEquals NaNNaN
等於 PositiveInfinityEquals PositiveInfinityPositiveInfinity

範例

正方形區域的平方根代表正方形任一側的長度。The square root of the area of a square represents the length of any side of the square. 下列範例會顯示美國的某些城市區域,如果是由正方形表示,則會提供每個城市大小的印象。The following example displays the area of some cities in the United States and gives an impression of each city's size if it were represented by a square.

// Create an array containing the area of some squares.
Tuple<string, double>[] areas = 
               { Tuple.Create("Sitka, Alaska", 2870.3), 
                 Tuple.Create("New York City", 302.6), 
                 Tuple.Create("Los Angeles", 468.7), 
                 Tuple.Create("Detroit", 138.8), 
                 Tuple.Create("Chicago", 227.1), 
                 Tuple.Create("San Diego", 325.2) };

Console.WriteLine("{0,-18} {1,14:N1} {2,30}\n", "City", "Area (mi.)", 
                  "Equivalent to a square with:");

foreach (var area in areas)
  Console.WriteLine("{0,-18} {1,14:N1} {2,14:N2} miles per side", 
                    area.Item1, area.Item2, Math.Round(Math.Sqrt(area.Item2), 2));        

// The example displays the following output:
//    City                   Area (mi.)   Equivalent to a square with:
//    
//    Sitka, Alaska             2,870.3          53.58 miles per side
//    New York City               302.6          17.40 miles per side
//    Los Angeles                 468.7          21.65 miles per side
//    Detroit                     138.8          11.78 miles per side
//    Chicago                     227.1          15.07 miles per side
//    San Diego                   325.2          18.03 miles per side
Module Example
   Public Sub Main()
      ' Create an array containing the area of some squares.
      Dim areas() As Tuple(Of String, Double) = 
                     { Tuple.Create("Sitka, Alaska", 2870.3), 
                       Tuple.Create("New York City", 302.6), 
                       Tuple.Create("Los Angeles", 468.7), 
                       Tuple.Create("Detroit", 138.8), 
                       Tuple.Create("Chicago", 227.1), 
                       Tuple.Create("San Diego", 325.2) }

      Console.WriteLine("{0,-18} {1,14:N1} {2,30}", "City", "Area (mi.)", 
                        "Equivalent to a square with:")
      Console.WriteLine()
      For Each area In areas
        Console.WriteLine("{0,-18} {1,14:N1} {2,14:N2} miles per side", 
                          area.Item1, area.Item2, Math.Round(Math.Sqrt(area.Item2), 2))        
      Next
   End Sub
End Module
' The example displays the following output:
'    City                   Area (mi.)   Equivalent to a square with:
'    
'    Sitka, Alaska             2,870.3          53.58 miles per side
'    New York City               302.6          17.40 miles per side
'    Los Angeles                 468.7          21.65 miles per side
'    Detroit                     138.8          11.78 miles per side
'    Chicago                     227.1          15.07 miles per side
'    San Diego                   325.2          18.03 miles per side

適用於

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