# Introduction to Programming (Lab Tutorial 8)

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```					            ENGI 1020
Introduction to Programming
(Lab Tutorial 8)

Memorial University of Newfoundland
Dr. Lihong Zhang

1
Lab Tutorial 8

Some Mistakes in Assignment 7
while (selection>=0 && selection <=3); //range of values
do {
……
}

i) while (…) {                 ii) do {
…                            …
}                             } while (…) ;

ENGI 1020 – Introduction to Programming                     2
Lab Tutorial 8

“break” and “continue”

while (…) {                     while (…) {
…                               …
break;                          continue;
…                               …
}                               }

ENGI 1020 – Introduction to Programming                      3
Lab Tutorial 8

cout << "X = " << thickness << "m" << endl;
<< endl << endl;
⇒ cout << "X = " << thickness << "m" << endl <<
endl << endl;
cout << "X = " << X < < " m " << endl;
⇒ cout << "X = " << X << " m " << endl;
k = [x*H]/[A*(T2 - T1)];
⇒ k = (x*H)/(A*(T2 - T1));

ENGI 1020 – Introduction to Programming       4
Lab Tutorial 8

Assignment-8
Newton's method to find the roots of an equation f(x) = 0
The procedure is to repeatedly compute a new estimate of the
root, y, using a previous estimate of the root, x, and the
following computation: y = x - f(x)/f '(x),
where f '(x) is the derivative of f(x)
The user should be prompted for an initial estimate of the
root, tolerance, and maxIterations (in that order). The values
entered should be echoed as output. To test your program you
can use -1.5 as a first guess for the root; tolerance = 0.0001;
and maxIterations = 10
In the program the functions f(x) and f '(x) must be computed
by separate value-returning functions
ENGI 1020 – Introduction to Programming                     5
Lab Tutorial 8

Some Hints

f(x) = x2e-x-2
f ′(x) = 2xe-x - x2e-x
i) y = x - f(x)/f '(x)
ii) x = y
In the case of f '(x) = 0, your program should
print the (exact) warning message, "Method fails,
division by zero." and stop.

ENGI 1020 – Introduction to Programming             6
Lab Tutorial 8                              Example Format

Using the following data
Initial guess: -1.5
Tolerance: 0.0001, and
Maximum iterations: 10.

Stopped after 5 iterations.
The best estimate of root is -0.901201
ENGI 1020 – Introduction to Programming         7

```
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