MATLAB for Engineers, 5th Edition – Complete Solution Manual (Chapters 2–6) with Code Examples

Matlab for Engineers, 5th Edition
Chapter 2 Homework Solutions

clear,clc, format shortg



You can either solve these problems in the command window, using MATLAB® as an electronic
calculator, or you can create an M-file of the solutions. If you are solving these problems as a homework
assignment or if you want to keep a record of your work, the best strategy is to use an M-file, divided
into cells with the cell divider %%.

Problem 2.1
Predict the outcome of the following MATLAB® calculations. Check your results by entering the
calculations into the command window.

1 + 3/4


ans = 1.75

5*6*4/2


ans = 60

5/2*6*4


ans = 60

5^2*3


ans = 75

5^(2*3)


ans = 15625

1 + 3 + 5/5 + 3 + 1

ans = 9

(1 + 3 + 5)/(5 + 3 + 1)


ans = 1



Using Variables

Problem 2.2
Identify which name in each of the following pairs is a legitimate MATLAB® variable name. Test your
answers by using isvarname—for example,

1

,isvarname fred

Remember, isvarname returns a 1 if the name is valid and a 0 if it is not. Although it is possible
to reassign a function name as a variable name, doing so is not a good idea. Use which to check
whether the preceding names are function names—for example,

which sin

In what case would MATLAB®tell you that sin is a variable name, not a function name?

The legitimate Matlab names are: fred book_1 Second_Place No_1 vel_5 tan

isvarname fred


ans = 1

isvarname book_1


ans = 1

isvarname Second_Place


ans = 1

isvarname No_1


ans = 1

isvarname vel_5


ans = 1

isvarname tan %although tan is a function name it can be used as a variable name


ans = 1

isvarname fred! %! is not an allowed character


ans = 0

isvarname book-1 % - is not an allowed character


ans = 0

isvarname 2ndplace %variable names must start with a letter


ans = 0

isvarname #1 %# is not an allowed character


ans = 0

isvarname vel.5 % . is not an allowed character


ans = 0
2

, isvarname while %while is a reserved name


ans = 0


which tan % tan is a function name


built-in (C:\Program Files\MATLAB\R2016b\toolbox\matlab\elfun\@double\tan) % double method

which while %while is also a function name, but is reserved


built-in (C:\Program Files\MATLAB\R2016b\toolbox\matlab\lang\while)


%You can reassign a function name as a variable name
%For example
sin=3


sin = 3

%The which function now tells us sin is a variable
which sin


sin is a variable.

% Use the clear function to return sin to its function definition
clear sin
which sin

built-in (C:\Program Files\MATLAB\R2016b\toolbox\matlab\elfun\@double\sin) % double method



Scalar Operations and Order of Operations

Problem 2.3
Create MATLAB® code to perform the following calculations. Check your code by entering it into
MATLAB® and performing the calculations on your scientific calculator.

5^2


ans = 25

(5 + 3)/(5*6)


ans = 0.26667

sqrt(4+6^3) % or...


ans = 14.832

(4+6^3)^(1/2)


ans = 14.832
3

, 9*6/12 + 7*5^(3+2)


ans = 21880

1 + 5*3/6^2 + 2^(2-4) *1/5.5


ans = 1.4621



Problem 2.4

(a) The area of a circle is Define r as 5, then find the area of a circle, using MATLAB®.

r=5


r = 5


area=pi*r^2


area = 78.54


(b) The surface area of a sphere is . Find the surface area of a sphere with a radius of 10 ft.

r=10


r = 10

surface_area=4*pi*r^2


surface_area = 1256.6


(c) The volume of a sphere is 4/3pr2. Find the volume of a sphere with a radius of 2 ft.


r=2


r = 2

volume=4/3*pi*r^3


volume = 33.51



Problem 2.5
(a) The area of a square is the edge length squared (A = edge2). Define the edge length as 5, then find
the area of a square, using MATLAB®.

edge=5


edge = 5
4