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) /