Question

大神，求步骤！谢谢！

Answer 1

x->0
sin3x ~3x
cosx ~ 1- (1/2)x^2
1-cosx ~ (1/2)x^2

lim(x->0+) sin3x/√(1-cosx)
=lim(x->0+) 3x/[(√2/2)x ]
=3√2

追问

看不懂

追答

这是等价无穷小
Or
lim(x->0+) sin3x/√(1-cosx) (0/0)
=lim(x->0+) sin3x/√( 2[sin(x/2)]^2 )
=(1/√2) lim(x->0+) sin3x/(sin(x/2)
=(1/√2) lim(x->0+) (3x)/(x/2)
=3√2

Answer 2

定义一个全局变量的数组：
dim a(10) as integer

随机产生10个两位的素数，素数各不相同：
Dim a(10), x As Integer
Dim str As String = ""
Dim di As Boolean = True
Dim n As Integer
Dim sd As
For i = 1 To 10
Do
Do
Randomize()
n = Int(Rnd() * 100 + 10)
Loop Until IsSushu(n)
If i > 1 Then
For x = 1 To i - 1
If a(x) = n Then
di = False
End If
Next
End If
Loop Until di = True
a(i) = n
'str = str & a(i) & " "
Next

随机数升序排序：
For i = 1 To 10
For j = 1 To 10 - i
If a(j) > a(j + 1) Then
x = a(j + 1)
a(j + 1) = a(j)
a(j) = x
End If
Next j
Next i

For i = 1 To 10
str = str & a(i) & " "
Next

将升序的数组写入文件：
Dim file As New System.IO.StreamWriter("data1.txt")
file.WriteLine(str)
file.Close()

读取文件，并写入数组及降序排序：
Dim file As New System.IO.StreamReader("data1.txt")
Dim words As String = file.ReadToEnd()
file.Close()
Dim b() As String
Dim temp As Integer
Dim str1 As String
str1 = ""
b = Split(words, " ")
Dim c() As Integer

Dim l As Integer
l = UBound(b)
ReDim c(l)

For i = 1 To l
c(i) = Val(b(i - 1))
Next
For i = 1 To l
For j = 1 To l - i
If c(j) < c(j + 1) Then
temp = c(j + 1)
c(j + 1) = c(j)
c(j) = temp
End If
Next j
Next i
For i = 1 To l
str1 = str1 & c(i) & " "
Next
MsgBox(str1)

追问

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