Laboratory 2

LABORATORY OBJECTIVES

• This lab work is intended to give the students more insights on the Matlab environment and how to work more efficiently with the commands window.

• The work is organized in two parts :• Part 1 : guided work, where the students can work through

the examples or procedures seen during the lectures• Part 2 : graded tasks through which the students

demonstrate ability to apply what they learned independently.

PART 1 : GUIDED TASKS

A. Example• solving a quadratic equation using Matlab as a calculator• Imagine that an engineering problem led to the

following second degree polynomial : 3x2 – x +2 =0• Answer :• Compute descriminant : d=b2 – 4ac• If d=0 x1=x2=-b/2a• If d>0 x1,2=(-bd)/2a• If d<0 x1,2=(-b i d)/2a (complexe numbers)

• Using the commands window, enter the following commands :

• First use assignment statements to define the coefficients a, b, and c

• >> a=…… ;• >> b=……;• >> c=……;

• Next, compute the descriminant (don’t use the semi-column ; to display the value of d !) :

• >> d=………….• d = • …………

• Then, compute the solutions :• >> x1= ………………………• >> x2=………………………

• Note that in this example you have used Matlab as a calculator; Be informed that Matlab can solve this in a much simpler manner by the use of the function “roots” which will be studied later in the semester.

Part 1

B. Working efficiently with the commands window

Command Description

>> clc Erase the display content of the command window

>> clear Removes all variables from the memory.

>> clear x, y, z Clears/removes only variables x, y and z from the memory.

>> who Lists the variables currently in the workspace.

>> whos Displays a list of the variables currently in the memory and their size together with information about their bytes and class.

>> help commandDisplays the descriptions of the requested command and how to use it (syntaxe)

>> lookfor command Displays all locations (files, folders, commands) that relates to the requested command

• Type “whos” to display the list of all defined variables

• Clear the coefficients a, b, and c• See what happens when you type the following• >> a or >> b or >> c or >> d• Next type >> clear This should result in

deleting all variables !• Finally, enter >> clc to clear the screen display

Part 2 (Graded Tasks)

1. Matlab Mathematic Built-in functions

Part 2 (Graded Tasks)

• 2. Common Error

>> a=-3. 4;

>> 2a^2-3

>> b=COS(2a)

>> a/b=c

>> d=5*a+1.23e+(i*02)*b