Olympiad Maths Prep

Track / Stage 4 / 197 of 340 #457 of 2000

Problem 457

AMC 12 late, AIME early
Geometry Difficulty 4.8 Find the answer

Example 4. Find the volume of the ellipsoid enclosed by the ellipsoid surface x2a2+y2b2+z2c2=1\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}+\frac{z^{2}}{c^{2}}=1.

Official solution

Given s1=s2=0,s0=πab,h=2cs_{1}=s_{2}=0, s_{0}=\pi a b, h=2 c,
V=2c6(0+4πab+0)=43πabc \therefore V=\frac{2 c}{6}(0+4 \pi a b+0)=\frac{4}{3} \pi a b c \text {. }

In particular, when c=bc=b, we get the
volume of an ellipsoid of revolution (Example 2)
When a=b=c=Ra=b=c=R, we get
Vsphere =43πR3 .  V_{\text {sphere }}=\frac{4}{3} \pi R^{3} \text { . }

Using the formula for the volume of a frustum
we can also calculate the volume of solids of revolution
formed by rotating certain transcendental curves around
coordinate axes.

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.