Or: p. 109 qualifying conditions are given which rule my example out, but IT-hy glve a wrong definition in the first place? I suspect that it is in order to 21void an unwelcome d.z. The student who has worked right through the book should be competent to deal with certain problems : gradients of curves, areas under curves, the first mean-value theorem, Taylor's theorern ( w~t h remainder), tangent planes to surfaces, and volumes under surfaces. But what about a simple volume of revolution or a

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... entre of gravity? With dx banished, it is not easy to see hov one is going to set about such problems. Large sections of the book are concerned with ideas about functions and