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gibson:teaching:fall-2014:math445:hw1

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====== Math 445 HW1 ====== Solve the following problems with Matlab. Save your Matlab session to a file by turning "diary on". When you're done, edit the diary in a text editor to remove errors and add appropriate comments. Print the edited diary to turn in. If you have your own computer and want to run Matlab on it, download and install Matlab from {{http://at.unh.edu/acs/services/software/ | UNH academic software}}. Otherwise you can do your homework on the computers in Kingsbury N129. Remember, you are required to do these homeworks **by yourself**. **Problem 1:** Given two numeric variables $x$ and $y$, write a Matlab expression that evaluates to true (1) if $x$ and $y$ have opposite signs and false (0) otherwise. By opposite signs, I mean one is positive and one is negative. Test the expression by evaluating it with the following pairs of numbers (x,y) = (-5, 4), (5,4), (5,-4), (0,-2), and (3,0). **Problem 2:** The combined resistance $R_T$ of three resistors $R_1, R_2, R_3$ in parallel is given by \begin{eqnarray*} R_T = \frac{1}{\frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}} \end{eqnarray*} Create variables for the three resistors $R_1, R_2, R_3$, with values 5, 3, and 4. Then calculate $R_T$ by translating the above formula into Matlab syntax. ** Problem 3:** \\ **(a)** Create a row vector x whose elements are the numbers 5, 7, 10, 1.\\ **(b)** Create a column vector x whose elements are the numbers 5, 7, 10, 1.\\ **%%(c)%%** Use colon syntax to create a row vector x whose elements start at 0, end at 1, and increase in steps of 0.1.\\ **(d)** Determine the dimension of x from %%(c)%% and assign the value to the variable d (using Matlab, not by counting!).\\ **(e)** Use the ''linspace'' function to create a 10-dimensional vector of numbers evenly spaced between 0 and 1. ** Problem 4:** \\ **(a)** Create the matrix A \begin{eqnarray*} A = \left[ \begin{array}{rrr} 3 & 9 & 2 \\ -1 & 4 & 6 \\ 5 & -2 & 0 \end{array} \right] \end{eqnarray*} **(b)** Change $A_{2,3}$ to 7.\\ **%%(c)%%** Assign the third column of A to the variable v.\\ **(d)** Change the first row of A to 8, 1, 4\\

gibson/teaching/fall-2014/math445/hw1.1409877049.txt.gz · Last modified: 2014/09/04 17:30 by gibson