Solution :
Here, we need to perform JOIN operation of the students and registration.
Use NATURAL JOIN operator 
and so no need to specify Join condition.
Also we need to selection operator tp select only those course whose major in "philosophy".
Finally we projection operator π to project only distinct students name who took at least three courses.
![$\pi [\sigma_{\text{student's nam}e} [ \sigma(\text{three courses}) \Join \text{"Philosophy"}]]$](https://tex.z-dn.net/?f=%24%5Cpi%20%5B%5Csigma_%7B%5Ctext%7Bstudent%27s%20nam%7De%7D%20%5B%20%5Csigma%28%5Ctext%7Bthree%20courses%7D%29%20%5CJoin%20%5Ctext%7B%22Philosophy%22%7D%5D%5D%24)
Answer: Well known ports
Explanation:
DHCP server transmit the response to the dynamic host configuration server protocol (DHCP) clients. DHCP default port is 67 and its port number is greater than the user data-gram specific port.
FTP server has its default listen at port 21 and file transition protocol(FTP) uses two transmission control protocol(TCP) connection for communication in the network. FTP passes information in port number 21, which is only used to send control information.
Well known port are use to identify the service of network on the public internet and private internet network. Therefore, port 21 and 67 are the well known ports.
Answer:
Visual.
Explanation:
Some programmers include scroll bars, title bars, buttons, and menus in a program simply by adding them to a layout through a process called visual programming.
A visual programming language is also commonly referred to as graphics user interface builder (GUI builder) and can be defined as a programming tool that avails programmers the ability to develop software programs (applications) using graphical elements and figures rather than texts alone.
Some examples of visual programming language are executable UML, Blockly, Kodu, Alice, Lego mindstorms, Gamemakers etc.
Answer:
The operation of 6*x only executes if x is greater or equal to 0, since x=-10 and -10 is less than 0, the operation does not execute. For this reason, the value of y using this code is None.
Explanation:
In python a function is defined with the syntaxis:
def function(x):
the operation to execute (x)
value to return
In this case, the function is foo and the parameter is x:
def foo(x):
if x>= 0:
return 6*x
The code starts by assigning a value to x. Then, the code asks if the value of x is grater or equal to 0, if this condition is meet, then the code returns the value of 6 times x, if not, then the code does not return a value. In this case, x is -10 and this value is not grater or equal to 0. Given that the condition is not met, then the code stops executing and the value of y is none.
Resheach thngs that instrest him and that fit the guidlines
