[tex]A_{romb}=\frac{d_1\cdot d_2}{2} =\frac{6\cdot12}{2} =6\cdot6=36\,cm^2[/tex]
[tex]A_{\bigtriangleup\:echilateral}=\frac{l^2\sqrt{3} }{4} =\frac{6^2\sqrt{3} }{4} =\frac{36\sqrt{3} }{4} =9\sqrt{3} \,cm^2[/tex]
[tex]A_{\bigtriangleup\:dreptunghic}=\frac{c_1\cdot c_2}{2} =\frac{8\cdot16}{2} =8\cdot8=64\,cm^2[/tex]
