a)A=(c₁xc₂)/2
A=(2,7cmx2,7 cm)/2=7,29/2=3,645 cm²
b)
A=(3,7cmx3,7cm)/2=13,69/2=6,845 cm²
c)
A=[(2+√3)(2+√3)]/2=(4+4√3+3)/2=(7+4√3)/2
d)
(√5+2)/(√5-2)=(√5+2)(√5+2)/5-4=(5+4√5+4)/1=8+4√5
A=[(8+4√5)(8+4√5)]/2=(64++64√5+80)/2=(144+64√5)/2=2(72+32√5)/2=
=72+32√5=8(9+4√5)