题干

已知圆C和y轴相切,圆心在直线x﹣3y=0上,且被直线y=x截得的弦长为27
(1)求圆C的方程.
(2)若圆心在第一象限,求过点(6,5)且与该圆相切的直线方程.
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答案(点此获取答案解析)

解:(1)设圆心为(3t,t),半径为r=|3t|,

则圆心到直线y=x的距离 d=3t-t2

同类题1

阅读理解

    When Jeanne Calment entered the world in 1875, telephones and automobiles still lay in the future. Albert Einstein and Pablo Picasso were not yet born. The Eiffel Tower was 14 years from being built. As a teenager, she met Vincent Van Gogh, near her home in Arles, in the south of France. He was “very ugly, ungracious, impolite, sick—I forgive him, they called him loco (精神失常的)”, she recalled. When she died last week at age 122, she was the world's eldest person. (There are others who claimed to the title, but only Calment had the official documents to prove her age.)

    Each February 21, her birthday, she would share the secrets of long life. Some years it was “a sense of humour”, others it was “keeping busy”. “God must have forgotten me,” she once explained. The truth probably was that her mother reportedly lived to be 86 and her father 94.

    Her life had its sadness: she outlived her husband, her only daughter and her grandson. According to a friend, she was imperturbable. “If you can't do anything about it,” she reportedly said, “don't worry about it.”

    In her last years she was nearly blind and deaf, but her health remained good. She ate a few bars of chocolate each week and continued smoking until a few years ago, when she could no longer light her own cigarettes. She never lost her sense of humour. On her 110th birthday, she commented, “I've only ever had one wrinkle, and I'm sitting on it. “Her longevity made her famous; her spirit made her eternal (永恒的).

同类题4

从产品库里面的product数据表中读出产品信息(ID,类别,产品名,图片路径,格式5个字段)。已知product表中已经按ID排序,读出后的数据直接连接成字符串在List1中显示,现在希望能不改变原有列表顺序的情况下,在list2中显示按产品名排序的结果。一般的方法是按产品名建立索引(不存在重复的产品名)。基本思路如下:

⑴用一个数组product()来存放产品名。

⑵用另一个数组a()来存放产品名数据的下标(已经按产品名排序的)。

按产品名排序的方法是:取第一个产品名product(0),与后面所有的产品名比较一遍,如果有比第一个产品名大的,M+1,M用来计该产品名的位次。一轮结束后在a(M)元素记下第一个产品名的下标0。然后再取product(1)与其它所有产品名比较一遍,其余同第一个产品名。依次完成每一个产品名位次的计算并记录在a()数组中。

⑶最后按a()数组指定的位置取出list1中的项添加到list2中。

程序代码如下,请补充完整下面的空缺。

Dim products(100) As String  '存放产品名的数组

Dim num As Integer          '从数据库中读出的记录数

Private Sub Command1_Click()

Dim a(100) As Integer           '存放按产品名索引的产品数组下标

Dim i As Integer, j As Integer, m As Integer    'm比当前产品名大的产品名个数

For i = 0 To 100

    a(i) = 0

Next i

For i = 0 To num

   m = 0

   For j = ____ 

     If i <> j And products(i) > products(j) Then m = m + 1

   Next j

   ____ 

Next i

For i = 1 To num

 List2.AddItem  ____     '按a数组的索引从list1中取出项添加到list2

Next i

End Sub

Private Sub Form_Load()

Dim conn As New ADODB.Connection

Dim rs As New ADODB.Recordset

Dim s As String, i As Integer

conn.ConnectionString = "provider=microsoft.ace.oledB.12.0;data source=" & App.Path & "\产品库.accdb "

conn.Open

Set rs.ActiveConnection = conn

rs.Open "select * from product"

num = 0

Do While Not rs.EOF And num <= 100

    s = ""

    For i = 1 To 5

     products(num) = rs.Fields(2)           '读出当前记录的产品名保存到products数组

     s = s & rs.Fields(i - 1) & " ,"        '将一条记录的各字段内容连接成字符串

    Next i

    List1.AddItem s

    ____

    num = num + 1

 Loop

 num = num - 1

 rs.Close

 conn.Close

 Set rs = Nothing

 Set conn = Nothing

End Sub