Hey all,
Since I am new to this forum I better intorduce myself first. Well, I plan to take C++ in June, but seeing it as being my weakness zone earlier on, I wanna train while I've got the chance. So, I'm studying on my own at home since uni doesn't start until summer, and I try to attempt a few questions. I'm gonna make a few topics so hope you all don't mind.

Here is my first problem and I'll show you how I've worked this out.

The value e^x can be approximated by the sum
1 + x + x^2/2! + x^3/3! + … + x^n/n!
Write a program that takes a value x as input and outputs this sum for n taken to be each of the values 1 to 100. The program should also output e^x calculated using the predefined function exp. The function exp is a predefined function such that exp(x) returns an approximation to the value ex. The function exp is in the library with the header file cmath. Your program should
repeat the calculation for new values of x until the user says she or he is through. 100 lines of output might not fit comfortably on your screen. Output the 100 output values in a format that will fit all 100 values on the screen. For
example, you might output 10 lines with 10 values on each line.

Okay, so there's basically three parts to this: first get the 100 values, then make them fit on the screen properly, and finally, to ask the user if he or she wants to repeat the calculation for another value of x.

Thusfar, I've done the first 2 things : get the 100 values and then display them in a 10 x 10 grid. I can show you guys my source code. Its as follows:

#include <iostream>
#include <cmath>
using namespace std;
int main ()
double x; //value input by the user
int i=1,counter=0;; /*counter from 1-100 is counter, i will be used to display text in an 
array */
double fact=1; //factorial
double ex=0; //this stores the answer for ex
cout << "This program will take a value x from you and will use it to find the"; 
cout << " approximation value of the expression e^x." << endl;
cout << "Please enter any real number value for x" << endl;
cin >> x; //takes the value x from the user
cout << "Displaying all values from x and entering into the equation" <<  endl; 
ex += pow(x,counter)/fact; //calculation for ex
counter++; //increment counter
fact*=counter; //calculation for factorial (counter!)
cout << "The calculated value for counter = 100 is "<<ex<<endl; 
cout << "The predefined value is " << exp(1) << endl;
system ("pause");
return 0;

My questions now:

1. Is this correct thusfar?
2. How do I modify the loop or add a loop so that the user can repeat the calculation with new values of x? I'm kinda stuck on that one..... if someone can modify my code I'd be grateful.

9 Years
Discussion Span
Last Post by wazcreliars

That function is gonna grow huge real quick.

Will you be able to get to n = 100 with the cmath library. Hmm?


Your calcution has counter running from 0 to 100, which will give you 101 terms rather than 100, but other than that it looks okay at first blush. Run your program to see what happens.

To allow the user to try out different values of x you just put the desired parts in a loop, say from here

cout << "Please enter any real number value for x" << endl;

to here

cout << "The predefined value is " << exp(1) << endl;

and reset the necessary values to their default value each time through the whole loop. You will also need some mechanism to break out of the loop when the user wants, but you can come up with that.


using turbo c... #include<stdio>.h

1. write a program that inputs two real numbers then exchanges their values.

2. make a program that will convert an inputted number in inches and display its equivalent measure in feet(ft).

3. create a program that will input a number in kilowatt and displays its equivalent measure in watts.


I will introduce my self into all you, hope that you don't mind about what did i posted here, I will wait your response hope so?!

thanks I am taking now a C++ by the degree of my study this problem probably needed tommorow...!?

thanks to all of you advance!?

1. Create a program that asks for a distance in kilometers and converts it into metric equivalent.

2. Write a program that will compute and display the midterm grade of a student. The midterm grade is equal to 1/3 of the minor A exam and 2/3 of the minor B exam.

3. Create a program that will input a number in Kilowatt and display its equivalent measure in watts.

4. Make a program that will convert an inputted number in inches and display the equivalent measure in feet.

5. Write a program that inputs two real numbers then exchanges their values.

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