P tr. dreptunghic = c1 + c2 + ip = AB + AC + BC = 30 cm
c1= cateta AB, c2 = cateta AC, ip = ipotenuza BC
AB² + AC² + BC² = 338 cm²
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A = ?
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A tr. dreptunghic = ( c1 · c2) supra 2
folosim formula de calcul prescurtat
( a + b + c )² = a² + b² + c² + 2ab + 2ac + 2bc
inlocuim pe a = AB, b = AC, c = BC
( AB + AC + BC)² = AB² + AC² + BC² + 2AB·AC + 2AB·BC + 2AC·BC
30² = 338 + 2AB·AC + 2AB·BC + 2AC·BC
900 - 338 = 2( AB·AC + AB·BC + AC·BC)
2( AB·AC + AB·BC + AC·BC) = 562
AB·AC + AB·BC + AC·BC = 562:2
AB·AC + AB·BC + AC·BC = 281
