29.28. Calculate the volume $V$ of a cone with radius $R$ and height $h$ using a definite integral.
29.28. Answer: $\frac{1}{3} \pi R^{2} h$. Let's choose the $O x$ axis as the axis of the cone and place the origin of the coordinates at the vertex of the cone. Then $V=\int_{0}^{h} \pi\left(\frac{R}{h} x\right)^{2} d x=\frac{1}{3} \pi R^{2} h$.