Function sec_rrule 

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

Reverse rule for sec.

Examples

use chainrules::sec_rrule;
let dy = sec_rrule(0.5_f64, 1.0);
assert!((dy - (0.5_f64.sin() / 0.5_f64.cos().powi(2))).abs() < 1e-12);