click a field, then use ⌨ keyboard · x is the variable · * for multiply · ^ for power · inner = 0 for disk
disk: y = √x
V = π ∫₀⁴ (√x)² dx
Volume ≈ 25.13
outer curve f(x)
inner curve g(x)
completed washer
active washer (gold edges)
axis of rotation (x)