$\displaystyle Tan(\frac{4\pi}{3}-\frac{\pi}{4}) = \frac{Tan(\frac{4\pi}{3})-Tan(\frac{\pi}{4})}{1+Tan(\frac{4\pi}{3}Tan(\frac{ \pi}{4})}=\frac{\sqrt{3}-1}{1+\sqrt{3}*1}= I do not know this step = 2-\sqrt{3}$

Could someone tell me what happens to take it from $\displaystyle \frac{\sqrt{3}-1}{1+\sqrt{3}*1} = 2-\sqrt{3}$