tan（π/3＋π/4）=tan(7π/12)=tan(π/4+π/3)=(tan(π/4)+tan(π/3))/(1-tan(π/4)tan(π/3))=(1+√3)/(1-√3)=(1+√3)²/(1-3)=-(1+3+2√3)/2=-2-√3