[tex]\displaystyle\\
\text{Aplicam reciproca teoremei lui Pitagora.}\\\\
a)\\
{\sqrt{AB^2+AC^2}=\sqrt{6^2+8^2}=\sqrt{36+64}=\sqrt{100}=10=BC}\\ \Longrightarrow m(\sphericalangle BAC)=90^o \\\\
b)\\
{\sqrt{AB^2+AC^2}=\sqrt{5^2+12^2}=\sqrt{25+144}=\sqrt{169}=13=BC}\\ \Longrightarrow m(\sphericalangle BAC)=90^o \\\\
c)\\
{\sqrt{AB^2+AC^2}=\sqrt{18^2+24^2}=\sqrt{324+576}=\sqrt{900}=30=BC}\\ \Longrightarrow m(\sphericalangle BAC)=90^o \\\\
[/tex]
