[ot][ot][ot][personal] whirligig small thoughts

[Undescribed Horrific Abuse, One Victim & Survivor of Many]

so i figured out these, i did the area of a circle by integrating arcs
approximating them as triangles with a base of dtheta.

area of circle = pi r^2
circumference of circle = 2pi r

the nice thing is that the area of the circle can be recast as equal
to other integral expressions over the circle, which hopefully lets us
quickly derive integration equations to reuse when sovling expressions
for the volume of a sphere