Folosim formula lui Heron :
[tex]a = 7 \: cm[/tex]
[tex]b = 24 \: cm[/tex]
[tex]c = 25 \: cm[/tex]
[tex]p = \frac{a + b + c}{2} [/tex]
[tex]p = \frac{7 + 24 + 25}{2} [/tex]
[tex]p = \frac{56}{2} [/tex]
[tex]p = 28\:cm[/tex]
[tex]A = \sqrt{p(p - a)(p - b)(p - c)} [/tex]
[tex]A = \sqrt{28(28 - 7)(28 - 24)(28 - 25)} [/tex]
[tex]A = \sqrt{28 \times 21 \times 4 \times 3} [/tex]
[tex]A = \sqrt{28} \times \sqrt{21} \times \sqrt{4} \times \sqrt{3} [/tex]
[tex]A = 2 \sqrt{7} \times \sqrt{21} \times 2 \times \sqrt{3} [/tex]
[tex]A = 4 \sqrt{7 \times 3 \times 21} [/tex]
[tex]A = 4 \sqrt{21 \times 21} [/tex]
[tex]A = 4 \times 21[/tex]
[tex]A = 84 \: {cm}^{2} [/tex]
