Average Error: 14.2 → 0.3
Time: 1.3m
Precision: 64
Internal Precision: 128
\[\left(\frac{\pi}{2} \cdot \frac{1}{b \cdot b - a \cdot a}\right) \cdot \left(\frac{1}{a} - \frac{1}{b}\right)\]
\[\frac{\pi}{b + a} \cdot \frac{1}{\left(a \cdot b\right) \cdot 2}\]

Error

Bits error versus a

Bits error versus b

Derivation

  1. Initial program 14.2

    \[\left(\frac{\pi}{2} \cdot \frac{1}{b \cdot b - a \cdot a}\right) \cdot \left(\frac{1}{a} - \frac{1}{b}\right)\]
  2. Using strategy rm
  3. Applied frac-sub14.2

    \[\leadsto \left(\frac{\pi}{2} \cdot \frac{1}{b \cdot b - a \cdot a}\right) \cdot \color{blue}{\frac{1 \cdot b - a \cdot 1}{a \cdot b}}\]
  4. Applied associate-*l/14.2

    \[\leadsto \color{blue}{\frac{\pi \cdot \frac{1}{b \cdot b - a \cdot a}}{2}} \cdot \frac{1 \cdot b - a \cdot 1}{a \cdot b}\]
  5. Applied frac-times14.2

    \[\leadsto \color{blue}{\frac{\left(\pi \cdot \frac{1}{b \cdot b - a \cdot a}\right) \cdot \left(1 \cdot b - a \cdot 1\right)}{2 \cdot \left(a \cdot b\right)}}\]
  6. Simplified0.2

    \[\leadsto \frac{\color{blue}{\frac{\pi}{b + a}}}{2 \cdot \left(a \cdot b\right)}\]
  7. Using strategy rm
  8. Applied div-inv0.3

    \[\leadsto \color{blue}{\frac{\pi}{b + a} \cdot \frac{1}{2 \cdot \left(a \cdot b\right)}}\]
  9. Final simplification0.3

    \[\leadsto \frac{\pi}{b + a} \cdot \frac{1}{\left(a \cdot b\right) \cdot 2}\]

Reproduce

herbie shell --seed 2019089 
(FPCore (a b)
  :name "NMSE Section 6.1 mentioned, B"
  (* (* (/ PI 2) (/ 1 (- (* b b) (* a a)))) (- (/ 1 a) (/ 1 b))))