Raza cercului circumscris in triunghi:
[tex]\frac{a}{sinA}= \frac{b}{sinB}= \frac{c}{sinC}=2R & \ \Leftrightarrow & \ \frac{BC}{sinA}= \frac{AC}{sinB}= \frac{AB}{sinC}=2R [/tex]
[tex]R = \frac{a\cdot b\cdot c}{4\cdot S_{\Delta ABC} } & \ \Leftrightarrow & \ R = \frac{BC\cdot AC\cdot AB}{4\cdot S_{\Delta ABC} }[/tex]
Raza cercului inscris in triunghi:
[tex] r = \frac{S_{\Delta ABC }}{P_{\Delta ABC}} [/tex]
[tex]r = 4R\cdot sin \frac{\hat A}{2} \cdot sin \frac{\hat B}{2} \cdot sin \frac{\hat C}{2}[/tex]
