Solucionario Calculo Una Variable Thomas Finney Edicion 9 179 -

Finally, the maximal volume:

Plugging this back into the expression for :

Simplifying gave

On the central table lay a battered copy of Thomas’ Calculus, 9th edition , its corners softened by years of eager thumbs. A thin, yellowed sheet was tucked between pages 178 and 180, its header scrawled in a hurried hand: . Maya’s professor had hinted that the problem was a “real gem” and that the solution would be discussed the next week—if anyone could actually work it out.

[ V'(x) = \frac{4x\bigl(R^2 - \tfrac{x^2}{2}\bigr) - x^3}{\sqrt{R^2 - \tfrac{x^2}{2}}} = \frac{4xR^2 - 2x^3 - x^3}{\sqrt{R^2 - \tfrac{x^2}{2}}} = \frac{4xR^2 - 3x^3}{\sqrt{R^2 - \tfrac{x^2}{2}}}. ] Finally, the maximal volume: Plugging this back into

She felt a surge of satisfaction. The problem had been reduced to a single‑variable function, exactly as the title promised. The next step was to find the maximum of (V(x)). Maya knew she needed the derivative (V'(x)) and the critical points where it vanished (or where the derivative was undefined). She set her mind to the task.

Now the volume of the box was simply

When she stood, the room fell silent. She described the geometry, the substitution of , the elegant reduction to a single‑variable function, and the calculus steps that led to the cube. She finished with the final expression (\displaystyle V_{\max}= \frac{8R^3}{3\sqrt{3}}) and a quick sketch of the inscribed cube inside the sphere.

which simplified to