7.
如图\(1\),点\(D\)为\(\triangle ABC\)边\(BC\)的延长线上一点.
\((1)\)若\(\angle A:\angle ABC=3:4\),\(\angle ACD=140{}^\circ \),求\(\angle A\)的度数;
\((2)\)若\(\angle ABC\)的角平分线与\(\angle ACD\)的角平分线交于点\(M\),过点\(C\)作\(CP⊥BM\)于点\(P\).求证:\(\angle MCP=90{}^\circ -\dfrac{1}{2}\angle A\);
\((3)\)在\((2)\)的条件下,将\(\triangle MBC\)以直线\(BC\)为对称轴翻折得到\(\triangle NBC\),\(\angle NBC\)的角平分线与\(\angle NCB\)的角平分线交于点\(Q(\)如图\(2)\),试探究\(∠BQC\)与\(∠A\)有怎样的数量关系,请写出你的猜想并证明.