$A=-\cos \alpha +\sin \alpha +(\cos \alpha )(-\sin \alpha )$

$\Rightarrow A=-\cos \alpha +\sin \alpha -\sin \alpha \cos \alpha $

$\cot \alpha =\frac{4}{3},-5\pi \lt \alpha \lt -\frac{9\pi }{2}$

$1+{{\cot }^{2}}\alpha =\frac{1}{{{\sin }^{2}}\alpha }\Rightarrow 1+\frac{16}{9}=\frac{1}{{{\sin }^{2}}\alpha }$

$\Rightarrow {{\sin }^{2}}\alpha =\frac{9}{25}\Rightarrow {{\sin }^{2}}\alpha =\pm \frac{3}{5}\xrightarrow[\sin \alpha \lt 0]{\alpha }\sin \alpha =-\frac{3}{5}$

$\Rightarrow {{\cos }^{2}}\alpha =1-{{\sin }^{2}}\alpha =1-\frac{9}{25}=\frac{16}{25}\Rightarrow \cos \alpha =\pm \frac{4}{5}$

ربع سوم $\alpha \Rightarrow \cos \alpha =-\frac{4}{5}$

$\Rightarrow A=-(-\frac{4}{5})+(-\frac{3}{5})-(-\frac{3}{5})(-\frac{4}{5})$

$\Rightarrow A=(\frac{4}{5}-\frac{3}{5})-\frac{12}{25}\Rightarrow A=-\frac{7}{25}=-0/28$