If you type in a valid expression and press Enter, MATLAB will immediately execute it and return the result.

>> 2+2

ans =

4

>> 4Ë†2

ans =

16

>> sin(pi/2)

ans =

1

>> 1/0

Warning: Divide by zero.

ans =

Inf

>> exp(i*pi)

ans =

-1.0000 + 0.0000i

Notice some of the special expressions here: pi for Ï€, Inf for ∞, and i for √−1. Another is NaN, which stands for not a number. NaN is used to express an undefined value. For example,

>> Inf/Inf

ans =

NaN

You can assign values to variables.

>> x = sqrt(3)

x =

1.7321

>> 3*z

??? Undefined function or variable ’z’.

Observe that variables must have values before they can be used. When an expression returns a single result that is not assigned to a variable, this result is assigned to ans, which can then be used like any other variable.

>> atan(x)

ans =

1.0472

>> pi/ans

ans =

3

In floating-point arithmetic, you should not expect “equal” values to have a difference of exactly zero. The built-in number eps tells you the maximum error in arithmetic on your particular machine. For simple operations, the relative error should be less than this number. For instance,

>> exp(log(10)) - 10

ans =

1.7764e-15

>> ans/10

ans =

1.7764e-16

>> eps

ans =

2.2204e-16

Here are a few other demonstration statements.

>> % This is a comment.

>> x = rand(100,100) ; % ; means "don’t print out"

>> s = ’Hello world’ ; % quotes enclose a string

>> t = 1 + 2 + 3 + ...

4 + 5 + 6 % ... continues a line

t =

21

Once variables have been defined, they exist in the workspace. You can see what’s in the

workspace from the desktop or by using

>> who

Your variables are:

ans s t x

**How to save work ?**If you enter save myfile, all the variables in the workspace will be saved to a file myfile.mat

in the current directory. Later you can use load myfile to recover the variables.

If you right-click in the Command History window and select “Create M-File. . . ”, you can

save all your typed commands to a text file. This can be very helpful for recreating what you have done.

**Q:**Evaluate the following mathematical expressions in MATLAB

---- tanh(e)

---- log10 (2)

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