Given a quadrilateral \(ABCD\) with all angles less than \(180^{\circ}\), \(\sphericalangle A=\sphericalangle B\), \(BC=1\) and \(AD=3\). Prove that \(CD>2\).

Dots četrstūris \(ABCD\), kuram visi leņķi ir mazāki nekā \(180^{\circ}\), \(\sphericalangle A=\sphericalangle B\), \(BC=1\) un \(AD=3\). Pierādīt, ka \(CD>2\).