Fundamental Commands

To define a constant, use a single equals sign:

You can include text by using Command 7

Once defined, you can use the constant anywhere you want:

To avoid problems,  erase from memory  the assigned value to a

When defining a function, you need to remember two important things:
    Use an underscore character after each argument name on the left-hand side (but not on the right-hand side)
    Use a := in the middle

To check your definition use the question mark before the name of a function
Once defined, you can use the function

?f

Global`f

You need to be carefull with User define functions.
For example we want to change the function

f[x_]:= x^2
?f

Global`f

Notice that the function was subtituted by the new definition. But now you change your mind and redefine the function

f[y_Integer] := y^3

?f

Global`f

Notice the two different definitions saved by MATHEMATICA.  One for real numbers and one for integers

{f[2],f[2.]}

Again, you change the definition of "f"

f[x_] := Sqrt[x]

?f

Global`f

f[4]

In order to avoid problems use Clear

Clear[f]
f[x_] := Sqrt[x]

?f

Global`f

The square root of 10

We need to tell MATHEMATICA that we need a numerical value.  We can use a decimal point

or we can use the N function and ask for 50 digits:

N[ Sqrt[10], 50 ]

3^100

N[%]

The command % refers to the previous output

In the following expression I stand for

(3 + 4 I) ^10

Created by Mathematica  (September 7, 2006)