Error

Derivation

1. Initial program 15.5

   \[\frac{r \cdot \sin b}{\cos \left(a + b\right)}\]
2. Using strategy rm

3. Applied cos-sum0.3

   \[\leadsto \frac{r \cdot \sin b}{\color{blue}{\cos a \cdot \cos b - \sin a \cdot \sin b}}\]
4. Using strategy rm

5. Applied *-un-lft-identity0.3

   \[\leadsto \frac{r \cdot \sin b}{\cos a \cdot \cos b - \color{blue}{1 \cdot \left(\sin a \cdot \sin b\right)}}\]

6. Applied *-un-lft-identity0.3

   \[\leadsto \frac{r \cdot \sin b}{\color{blue}{1 \cdot \left(\cos a \cdot \cos b\right)} - 1 \cdot \left(\sin a \cdot \sin b\right)}\]

7. Applied distribute-lft-out--0.3

   \[\leadsto \frac{r \cdot \sin b}{\color{blue}{1 \cdot \left(\cos a \cdot \cos b - \sin a \cdot \sin b\right)}}\]

8. Applied times-frac0.3

   \[\leadsto \color{blue}{\frac{r}{1} \cdot \frac{\sin b}{\cos a \cdot \cos b - \sin a \cdot \sin b}}\]

9. Simplified0.3

   \[\leadsto \color{blue}{r} \cdot \frac{\sin b}{\cos a \cdot \cos b - \sin a \cdot \sin b}\]

10. Taylor expanded around inf 0.3

    \[\leadsto \color{blue}{\frac{\sin b \cdot r}{\cos a \cdot \cos b - \sin b \cdot \sin a}}\]

11. Simplified0.4

    \[\leadsto \color{blue}{\frac{r}{\frac{\cos a}{\sin b} \cdot \cos b - \sin a}}\]

12. Final simplification0.4

    \[\leadsto \frac{r}{\frac{\cos a}{\sin b} \cdot \cos b - \sin a}\]

Reproduce

herbie shell --seed 2019088 +o rules:numerics
(FPCore (r a b)
  :name "r*sin(b)/cos(a+b), A"
  (/ (* r (sin b)) (cos (+ a b))))