1.
\((1)\)计算:\(\lg 4+\lg 9+2\sqrt{{{\left( \lg 6 \right)}^{2}}-\lg 36+1}=\)_____________
\((2)\)若角\(\alpha \)和\(\beta \)的终边关于直线\(x+y=0\)对称,且\(\alpha =-\dfrac{\pi }{3}\),则角\(\beta \)的集合是_____________
\((3)\)扇形\(AOB\)周长为\(8\),圆心角为\(2\)弧度,则其面积为________________
\((4)\)已知\(\sin ( \dfrac{π}{6}+α)= \dfrac{3}{5}, \dfrac{π}{3} < α < \dfrac{5π}{6} \),则\(\cos \alpha \)的值是_______________