tan(A+C)=-tanB=-根2/2 tanA+tanC=sinA/cosA+sinC/cosC=sin(A+C)/cosAcosC=根2/2/(cosAcosC)
又1/sin^2B=1/(sinAsinC)=2
上式为tanA+tanC=根2/2*2*sinAsinC/(cosAcosC)=根2tanAtanC
带入tan(A+C)展开式
结果=-1
tan(A+C)=-tanB=-根2/2 tanA+tanC=sinA/cosA+sinC/cosC=sin(A+C)/cosAcosC=根2/2/(cosAcosC)
又1/sin^2B=1/(sinAsinC)=2
上式为tanA+tanC=根2/2*2*sinAsinC/(cosAcosC)=根2tanAtanC
带入tan(A+C)展开式
结果=-1