1. Laboratory 2

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.

3. 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 : 3x 2 – x +2 =0 Answer : Compute descriminant : d=b 2 – 4ac If d=0  x1=x2=-b/2a If d>0  x1,2=(-b   d)/2a If d<0  x1,2=(-b  i  d)/2a (complexe numbers)

4. Using the commands window, enter the following commands : First use assignment statements to define the coefficients a, b, and c >> a=…… ; >> b=……; >> c=……;

5. Next, compute the descriminant (don’t use the semi-column ; to display the value of d !) : >> d=…………. d = …………

6. Then, compute the solutions : >> x1= ……………………… >> x2=………………………

7. 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.

8. 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 command Displays 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

9. 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

10. Part 2 (Graded Tasks) 1. Matlab Mathematic Built-in functions

11. 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