Aplicam teorema Lui Pitagora pentru a afla ipotenuza BC
[tex] BC^{2} = AC^{2} + AB^{2} BC^{2} =25+144=169=\ \textgreater \ BC= \sqrt{169} =13[/tex]
sin B=AC/BC=>sin B=5/13
sin C=AB/BC=>sin C=12/13
cos B=AB/BC=>cos B=5/13
tg C=AB/AC=>tg C=5/12
ctg B= AB/AC=>ctg B=5/12
[tex]sin^2 B+cos^2 B=AC^2/BC^2 +AB^2/BC^2=(AC^2+AB^2)/BC^2[/tex]
Din teorema lui pitagora avem [tex] AC^{2} + AB^{2} = BC^{2} [/tex]
[tex] sin^{2} B+ cos^{2} B=BC^2/BC^2=1(A)[/tex]
