Can you find the volume of a sphere?

We'll draw a triangle (ABC):

And we will use Pythagoras theorem to find BC: ${ BC }^{ 2 }={ AB }^{ 2 }\quad +\quad { AC }^{ 2 }\\ And\quad we\quad know:\quad AB=3cm\quad and\quad AC=4cm\\ Therefore:\\ BC^{ 2 }=\quad { 3 }^{ 2 }\quad +\quad { 4 }^{ 2 }\\ BC^{ 2 }=\quad 9\quad +\quad 16\\ BC^{ 2 }=\quad 25\\ BC=\quad \sqrt { 25 } \\ BC=\quad 5$

Also, we see from the figure that $BC= 4r$ , therefore $r=\quad \frac { BC }{ 4 } \\ r=\quad \frac { 5 }{ 4 } \\ r=1.25$

And we know:

${ V }_{ sphere }=\quad \frac { 4 }{ 3 } \pi { r }^{ 3 }$

So:

${ V }_{ sphere }\approx \quad 8.18$