2 1 - tanh (x) ------------ tanh(x)
2
/ 2 \
2 \-1 + tanh (x)/
-2 + 2*tanh (x) - ----------------
2
tanh (x) / 2 \
| / 2 \ / 2 \|
/ 2 \ | \-1 + tanh (x)/ 2*\-1 + tanh (x)/|
2*\-1 + tanh (x)/*|-2*tanh(x) - ---------------- + -----------------|
| 3 tanh(x) |
\ tanh (x) /