# Measuring volume of spheres using triple integrals

1. May 28, 2012

### robertjford80

1. The problem statement, all variables and given/known data

I'm just interested in knowing where the 4 comes from in front of the integral.

2. May 28, 2012

### tiny-tim

hi robertjford80!

that 4∫0π/2 is really ∫0

i suppose the writer thought it looks confusingly like ∫00, though i see nothing wrong with it!

3. May 28, 2012

### robertjford80

Ok, pretty unexpected but I guess it makes sense.

4. May 28, 2012

### HallsofIvy

In other words, they are using the circular symmetry of the figures, integrating from 0 to $\pi/2$, rather than from 0 to $2\pi$, then multiplying by 4.