平面上,\(Rt\triangle ABC\)与直径为\(CE\)的半圆\(O\)如图\(1\)摆放,\(∠B=90^{\circ}\),\(AC=2CE=m\),\(BC=n\),半圆\(O\)交\(BC\)边于点\(D\),将半圆\(O\)绕点\(C\)按逆时针方向旋转,点\(D\)随半圆\(O\)旋转且\(∠ECD\)始终等于\(∠ACB\),旋转角记为\(α(0^{\circ}\leqslant α\leqslant 180^{\circ})\).
\((1)\)当\(α=0^{\circ}\)时,连接\(DE\),则\(∠CDE=\)________\({\,\!}^{\circ}\),\(CD=\)________;
\((2)\)试判断:旋转过程中\(\dfrac{BD}{AE}\)的大小有无变化?请仅就图\(2\)的情形给出证明;
\((3)\)若\(m=10\),\(n=8\),当\(α=∠ACB\)时,求线段\(BD\)的长;
\((4)\)若\(m=6\),\(n=4 \sqrt{2} \),当半圆\(O\)旋转至与\(\triangle ABC\)的边相切时,直接写出线段\(BD\)的长.