Notăm măsurile unghiurilor cu x, y, z.
[tex]\it x+y+z=180^o\ \ \ \ (*)\\ \\ \{x,\ y,\ z\}\ d.\ p.\ \{3,\ 4,\ 5\} \Rightarrow \dfrac{x}{3}=\dfrac{y}{4}=\dfrac{z}{5}=\dfrac{x+y+z}{3+4+5}\stackrel{(*)}{=}\ \dfrac{180^o}{12}=15^o\Rightarrow\\ \\ \\ \Rightarrow \begin{cases}\it \dfrac{x}{3}=15^o \Rightarrow x=3\cdot15^o=45^o\\ \\ \it \dfrac{y}{4}=15^o \Rightarrow y=4\cdot15^o=60^o\\ \\ \it \dfrac{z}{5}=15^o \Rightarrow z=5\cdot15^o=75^o\end{cases}[/tex]
