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Rezolvati problema:
42. Aflati aria unui triunghi echilateral, care are inaltimea de 21 cm.


Răspuns :

nota latura=a
h=√a²-(a/2)²=√3a²/4=a√3/2
a√3/2=21
a=21×2/√3=42√3/3=14√3 cm
A=14√3×21/2=147√3 cm²