Function sech_rrule 

pub fn sech_rrule<S: ScalarAd>(x: S, cotangent: S) -> S

Reverse rule for sech.

Examples

use chainrules::sech_rrule;

let dy = sech_rrule(0.5_f64, 1.0);
let sech_x = 1.0 / 0.5_f64.cosh();
assert!((dy + sech_x * 0.5_f64.tanh()).abs() < 1e-12);