se aplica Teorema lui PitAGORA
[tex]A) AB^{2}= BC^{2}+AC^{2} \\ \\ AB= \sqrt{ BC^{2}+AC^{2} } = \sqrt{ 12^{2}+5^{2} } = \sqrt{144+25}= \sqrt{169}=13[/tex]
[tex]B) BC^{2}=AB^{2}-AC^{2} \\ \\ BC= \sqrt{ AB^{2}-AC^{2} } = \sqrt{ 20^{2}-16^{2} } = \sqrt{400-256}= \sqrt{144}=12[/tex]
[tex]C) AC^{2}= AB^{2}+BC^{2} \\ \\ AC= \sqrt{ AB^{2}-BC^{2} } = \sqrt{ 41^{2}-40^{2} } = \sqrt{1681-1600}= \sqrt{81}=9[/tex]
