dy dy dt
——— = ——— · ———
dx dt dx
1 (3λt^3 + 2κt^2 + (1 + 6λ)t + 2κ)
= —————— e^(—(t^2/2)) · ————————————————————————————————
√(2π) a(1 + 2κt + 3λt^2)
From the vanishing of the numerator of dy/dx there must result either
one or three real modes for each pair of values for λ and κ, that is,
for each translated curve. To determine what values of λ and κ give
uni-modal curves and what tri-modal it is convenient to consider the
plane of λ and κ.