[tex]L=2 \pi R~~~~~~~(u.l) \\ A= \pi R^{2} ~~~~~~~(u.a) \\ \\ 2 \pi R= \pi R ^{2} \Rightarrow 2= \frac{ \pi R^{2}}{ \pi R} \Leftrightarrow R=2~~~~~~(u.l) \\ \\ Deci~pentru~R=2~u.l,~aria~xi~lungimea~cercului~sunt~exprimate~ \\ prin~acelasi~numar. \\ \\ u.l.=unitati~de~lungime~ (mm,~cm,~dm,~m,~dam,~hm,~km)\\ u.a.=unitati~de~arie~(mm^2,~cm^2,~dm^2,~m^2,~dam^2,~hm^2,~km^2)[/tex]
