Page:Calculus Made Easy.pdf/122

 from the values calculated, as below, from the original equation.

A further exercise in maxima and minima is afforded by the following example:

The equation to a circle of radius $$r$$, having its centre $$C$$ at the point whose coordinates are $$x=a$$, $$y=b$$, as depicted in Fig. 29, is:

This may be transformed into



Now we know beforehand, by mere inspection of the figure, that when $$x=a$$, $$y$$ will be either at its maximum value, $$b+r$$, or else at its minimum value, $$b-r$$. But let us not take advantage of this