\(\int_{0}^{\pi /4}\left ( \frac{1-tan\, x}{1+tan\, x} \right )\) evaluates to
-
Solution
An unbalanced dice (with 6 faces, numbered from 1 to 6)is thrown. The probability that the face value is odd is 90%of the probability that the face value is even. The probability of getting any even numbered face is the same.If the probability that the face is even given that it is greater than 3 is 0.75, which one of the following options is closest to the probability that the face value exceeds 3 ?
How many solutions does the following system of linear equations have?
–x + 5y =–1
x – y = 2
x +3y = 3
-
Solution
E1 and E2 are events in a probability space satisfying the following constraints
Pr (E1) = Pr (E2)
Pr (E1 ∪ E2) =1
E1 and E2 are independent
The value of Pr(E1), the probability of the event E1, is______
-
Solution
1
Let Ax = b be a system of linear equations where A is an m × n matrix and b is a m × 1 column vector and X is an × 1 column vector of unknowns. Which of the following is false?
Suppose the round trip propagation delay for a 10 Mbps Ethernet having 48 bit jamming signal is 46.4 ms. The minimum frame size is
-
Solution
Transmission speed = 10 Mbps, Round trip propagation delay = 46.4ms. The minimum frame size= (Round Trippropagation delay) * (Transmission speed) =10 * (10 ^6) * 46.4 * (10 ^ –3)
= 464 * 10 ^ 3 = 464 kbits.
The maximum window size for data transmission using the selective reject protocol with n-bit frame sequence number is
-
Solution
Let us assume the following :
I Communication between two Stations; Station A and Station B
II The size of Window to be 8 (0, 1, 2, 3, 4, 5, 6, 7) Now, the communication between the two stations would be as follows:1.Station A sends frame 0 to Station B
2.Station B receives frame 0 and sends an acknowledgement(ack) as RR1
3.Station A sends frame 1 to Station B
4.Station B receives frame 1 and sends an acknowledgement(ack) as RR2
5.Station A sends frame 2 to Station B
6.Station B receives frame 2 and sends an acknowledgement(ack) as RR3
7.Station A sends frame 3 to Station B
8.Station B receives frame 3 and sends an acknowledgement(ack) as RR4
9.Station A sends frame 5 to Station B
10.Station B receives frame 5 and sends an acknowledgement(ack) as RR6
11.Station A sends frame 6 to Station B
12.Station B receives frame 6 and sends an acknowledgement (ack)as RR7
13.Now, RR7 is lost in the transmission. Since, Station A will send frame 7 only after receiving RR7, so it will Time Out as RR7 is already lost.
14.Now, A times out retransmit frame 015.But B was expecting frame 7, so it considers frame 7 as Lost and accept frame 0 as a new frame.
→This problem is overcome by limiting the maximum windows size to 2n–1
because in selective reject protocal maximum sizeof window must be half of the maximum sequence number.
Given the following relation instance:
X Y Z
1 4 2
1 5 3
1 6 3
3 2 2
Which of the following functional dependencies are satisfied by the instance?
-
Solution
A functional dependency (FD) is a constrant between two sets of attributes in a relation from a data base. A FD, x → y require that the value of x uniquly determines the value of y where x and y are set of attributes. FD is a generalization of the notion of a key. given that, x,y, and z are sets of attributes in relation R, one can drive several propeaties of functional dependency. Among the most important are Armstrongs axioms, which are used in database normalization. In this question, Y uniquely determines X and Z, for a given value of Y you can easily find out values of X and Z.
So, Y → X and Y → Z hold for this Schema.
From rule of augmenation we can say YZ → X, if we understand the notion of FD, we don’t need to apply axioms to find out the option (b) is true. because Y is functionally dependent on Z.
→ YZ is functionally dependent on X.
The employee information in a company is stored in the relation
Employee (name, sex, salary, deptName)
Consider the following SQL query :
Select dept Name
From Employee Where sex = ‘M’
Group by dept Name
Having avg (salary) >
(select avg (salary) from Employee)
It returns the name of the department in which
-
Solution
SQL query will compute as follows :
1. Selects the name from the department
2. Selects the male employee
3. Computes that
the average salary of male employees is more than the average salary in the company.
Which of the following scenarios may lead to an irrecoverable error in a database system?
-
Solution
A transaction reads a data item after it is written by an uncommitted transaction.As the errors cannot recovered in this situation.