Divas riņķa līnijas \(\omega_{1}\) (ar centru punktā \(O_{1}\)) un \(\omega_{2}\) (ar centru punktā \(O_{2}\)) krustojas punktā \(A\). Taisne \(O_{1} A\) krusto \(\omega_{2}\) punktā \(B_{2}\), bet \(\omega_{1}-\) punktā \(C_{1}\). Taisne \(O_{2}A\) krusto \(\omega_{1}\) punktā \(B_{1}\), bet \(\omega_{2}\) - punktā \(C_{2}\) (skat. 32.att.). Pierādīt, ka \(\sphericalangle B_{2}B_{1}A=\sphericalangle C_{2}C_{1}A\).