[tex]ctg\left(\dfrac{\pi}{4}-x\right)=\dfrac{1}{tg\left(\dfrac{\pi}{4}-x\right)}=\dfrac{1}{\dfrac{tg\dfrac{\pi}4-tgx}{1+tg\dfrac{\pi}4\cdot tgx}}=\dfrac{1+tg\dfrac{\pi}4\cdot tgx}{tg\dfrac{\pi}4-tgx}=\\\\\\=\dfrac{1+1\cdot 2}{1-2}=-3.[/tex]
Green eyes.
