2．
如图，\(N\)、\(S\)是球\(O\)直径的两个端点，圆\(C_{1}\)是经过\(N\)和\(S\)点的大圆，圆\(C_{2}\)和圆\(C_{3}\)分别是所在平面与\(NS\)垂直的大圆和小圆，圆\(C_{1}\)和\(C_{2}\)交于点\(A\)、\(B\)，圆\(C_{1}\)和\(C_{3}\)交于点\(C\)、\(D\)，设\(a\)、\(b\)、\(c\)分别表示圆\(C_{1}\)上劣弧\(CND\)的弧长、圆\(C_{2}\)上半圆弧\(AB\)的弧长、圆\(C_{3}\)上半圆弧\(CD\)的弧长，则\(a\)、\(b\)、\(c\)的大小关系为\((\) \()\)
