2.
I.设函数\(f(x)= \dfrac{1}{2}{x}^{2}−m\ln x \),\(g(x)=x^{2}-(m+1)x\),\(m > 0\).
\((\)Ⅰ\()\)求函数\(f(x)\)的单调区间;
\((\)Ⅱ\()\)当\(m\geqslant 1\)时,讨论函数\(f(x)\)与\(g(x)\)图象的交点个数.
\(II.\)如图,\(∠BAC\)的平分线与\(BC\)和\(\triangle ABC\)的外接圆分别相交于\(D\)和\(E\),延长\(AC\)交过\(D\)、\(E\)、\(C\)三点的圆于点\(F\).
\((\)Ⅰ\()\)求证:\(EC=EF\);
\((\)Ⅱ\()\)若\(ED=2\),\(EF=3\),求\(AC·AF\)的值.