%has to be completed

\documentclass{article}

\usepackage[nomessages]{fp}

\parskip0.5\baselineskip

\begin{document}

\FPadd\result{12.2}{7.1}	$12.2 + 7.1 = \result$

\FPsub\result{12.2}{7.1}	$12.2 - 7.1 = \result$

\FPmul\result{12.2}{7.1}	$12.2 * 7.1 = \result$

\FPdiv\result{12.2}{7.1} 	${12.2 \over 7.1} = \result$

\FPround\res{\result}{8}	$\mathop{round}({12.2 \over 7.1}) \mathbin{at} 8 = \res$

\FPtrunc\res{\result}{8}	$\mathop{trunc}({12.2 \over 7.1}) \mathbin{at} 8 = \res$

\FPadd\result{12.2}{7.1}
\FPclip\res{\result}		$\mathop{clip}({12.2 + 7.1})= \res$

\FPeval{res}{round(12/7:10)}    $\mathop{eval}(\verb+round(12/7:10)+) = \FPprint{res}$

\bigskip

Recommended usage of package for normal users: Use the macro eval!

\bigskip

\FPset{result}{5.22599}
\FPeval{res}{round(result:4)}	$\mathop{eval}(\verb+round(5.22599:4)+) = \FPprint{res}$

\FPeval{res}{trunc(result:4)}	$\mathop{eval}(\verb+trunc(5.22599:4)+) = \FPprint{res}$

\FPeval{res}{sin(12) * (-8)}	$\mathop{eval}(\verb+sin(12) * (-8)+) = \FPprint{res}$ 

Do not forget $($ and $)$ around negated values like $-8$ in the evaluation above.

\FPeval{res}{ln(pi * arctan(e))}$\mathop{eval}(\verb+ln(pi * arctan(e))+) = \FPprint{res}$ 

\end{document}