="inline_math">\( 0 \)</span> and <span class="inline_math">\( 1 \)</span> (<span class="inline_math">\( 0\leq \varepsilon &lt; 1 \)</span>).<span class="intersentencespace"></span> Note we include the case <span class="inline_math">\( \varepsilon=0 \)</span> since a circle is a special case of an ellipse.<span class="intersentencespace"></span> For a parabola, <span class="inline_math">\( q=f \)</span> (the focal length) and the eccentricity is <span class="inline_math">\( \varepsilon=1 \)</span>.<span cla