Question

Find the volume of the sphere of radius a with centre at origin

Answer 1

( figure is in the image)


since center is at origin so the coordinates of Centre will be (0,0) and let A (x,y)

BY APPLING DISTANCE FORMULA
$a = \sqrt{x {}^{2} + y {}^{2} }$
now,

vol. of sphere =
$\frac{4}{3} \times \pi \: r {}^{2}$
inserting value of r


$\frac{4}{3 } \times \pi \: ( \sqrt{x {}^{2} + y {}^{2} \: } ) {}^{2}$
that is


$\frac{4}{3} \pi \: x {}^{2} + y {}^{2}$