c=√(a^2+b^2)
=√(2√3+1)^2+(2√3-1)^2
=√(12+4√3+1)+(12-4√3+1)
=√26
面积
=1/2ab
=1/2×(2√3+1)×(2√3-1)
=1/2×(12-1)
=11/2