P. 167, lines -4,-3 and -2

The derivatives should be:

${\frac {df}{dt}}(t)=-{\frac {2t}{(1+t^{2})^{2}}}$

Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \frac{d^2f}{dt^2}(t) = \frac{6 t^2}{(1+t^2)^3 - \frac{2}{(1+t^2)^3}}

${\frac {d^{3}f}{dt^{3}}}(t)={\frac {24t^{2}}{(1+t^{2})^{4}}}-{\frac {24t}{(1+t^{2})^{4}}}$

Return to errata.