\section{Math functions}

\index{math function}

Python has a math module that provides most of the familiar

mathematical functions. A {\bf module} is a file that contains a

\index{sine function}

\index{radian}

\index{trigonometric function}

The second example finds the sine of {\tt radians}. The variable name {\tt radians} is a hint that {\tt sin} and the other trigonometric

functions ({\tt cos}, {\tt tan}, etc.) take arguments in radians. To

If you know

trigonometry, you can check the previous result by comparing it to

\index{sqrt function}

\index{function!sqrt}

\section{Fruitful functions and void functions}

\index{fruitful function}

\index{void function}

Some of the functions we have used, such as the math functions, return

results; for lack of a better name, I call them {\bf fruitful

\section{Why functions?}

It may not be clear why it is worth the trouble to divide

a program into functions. There are several reasons:

\section{Exercises}

are meant to be fun, but they have a point, too. While you are

working on them, think about what the point is.

The following exercises use the {\tt turtle} module, described in

Chapter~\ref{turtlechap}:

\begin{exercise}

I chose these values so that the horizontal distance is 3 and the

vertical distance is 4; that way, the result is 5, the hypotenuse

useful to know the right answer.

\index{testing!knowing the answer}