tanπ/12+cotπ/12=sinπ/12/cosπ/12+cosπ/12/sinπ/12=(sin²π/12+cos²π/12)/(sinπ/12cosπ/12)=1/[1/2*sin(2*π/12)]=1/(1/2*sinπ/6)=2/(1/2)=4
