Can someone help me with this? I'm confused about why pi,

why not? you have to somehow isolate the r^2
M=x*r^2
M/x=r^2
where x = pi*h*d

>>136932
Wow I'm retarded. Just realized what I did. Lol thanks!

>>136932
Wait, then why is M even multiplied by x?

>>136937
you multiply numerator and denominator with sqrt(pi*h*d)

>>136937
dunno, aesthetics maybe?

r^2=M/x |square root everything, which is equivalent to ^1/2
r=(M/x)^1/2 |now they (for whatever reason) don't seem to like having a square root in the denominator, so they expand the fraction by (x/x)^1/2 so the roots in the denomator cancel
r=(Mx)^(1/2)/x

>>136937
because you try to avoid doing divisions with a real number as divisor.

1/sqrt(2) = 1/1.41421356237... okay, give me some time and I can calculate it...

1/sqrt(2) = sqrt(2)/2 = 1.41421356237../2 = 0.70710678118...

you can simply write the answer if you know sqrt(2) (up to the desired precision).