[tex]\displaystyle\bf\\Se~da:\\Paralelogramul~ABCD~cu:~AE\perp BC~si~AF\perp CD\\AE~si~AF~sunt~inaltim~ale~paralelogramului\\\\AE = 5~cm,~AF = 6~cm~și~CD = 10~cm\\\\Se~cere:~BC=?\\\\Aria~paralelogramului~este:\\\\A_{ABCD}=B\times \^I\\\\A_{ABCD}=BC\times AE=CD\times AF\\\\Nu~calculam~aria~deoarece~nu~se~cere.\\\\BC\times AE=CD\times AF\\\\BC=\frac{CD\times AF}{AE}=\frac{10\times 6}{5}=\frac{60}{5}=\boxed{\bf12~cm}[/tex]
