Initial program 14.9
\[r \cdot \frac{\sin b}{\cos \left(a + b\right)}\]
- Using strategy
rm Applied cos-sum0.3
\[\leadsto r \cdot \frac{\sin b}{\color{blue}{\cos a \cdot \cos b - \sin a \cdot \sin b}}\]
- Using strategy
rm Applied flip--0.4
\[\leadsto r \cdot \frac{\sin b}{\color{blue}{\frac{\left(\cos a \cdot \cos b\right) \cdot \left(\cos a \cdot \cos b\right) - \left(\sin a \cdot \sin b\right) \cdot \left(\sin a \cdot \sin b\right)}{\cos a \cdot \cos b + \sin a \cdot \sin b}}}\]
- Using strategy
rm Applied *-un-lft-identity0.4
\[\leadsto r \cdot \frac{\sin b}{\color{blue}{1 \cdot \frac{\left(\cos a \cdot \cos b\right) \cdot \left(\cos a \cdot \cos b\right) - \left(\sin a \cdot \sin b\right) \cdot \left(\sin a \cdot \sin b\right)}{\cos a \cdot \cos b + \sin a \cdot \sin b}}}\]
Applied associate-/r*0.4
\[\leadsto r \cdot \color{blue}{\frac{\frac{\sin b}{1}}{\frac{\left(\cos a \cdot \cos b\right) \cdot \left(\cos a \cdot \cos b\right) - \left(\sin a \cdot \sin b\right) \cdot \left(\sin a \cdot \sin b\right)}{\cos a \cdot \cos b + \sin a \cdot \sin b}}}\]
Simplified0.3
\[\leadsto r \cdot \frac{\frac{\sin b}{1}}{\color{blue}{\cos b \cdot \cos a - \sin b \cdot \sin a}}\]
Final simplification0.3
\[\leadsto \frac{\sin b}{\cos a \cdot \cos b - \sin b \cdot \sin a} \cdot r\]