The sequence is times 2 minus 2
3 x 2 = 6 - 2 = 4
10 x 2 = 20
20 - 2 = 18
If you’re looking for the volume of a sphere, it is
V = 4/3πr³
I suppose the curve is
.
Tangent lines to the curve have slope
; use the chain rule to get this in polar coordinates.

We have




The tangent line is horizontal when the slope is 0, which happens wherever the numerator vanishes:


(where
is any integer)
The tangent line is vertical when the slope is infinite or undefined, which happens when the denominator is 0:


125
2^3 = 8
8 = 1/2 of 16
1/2 of 250 = 125