The function \(f\left( x \right) = \left\{ {\begin{array}{*{20}{c}} { - 2\;sin\;x}&{ - \pi \le x < - \frac{\pi }{2}}\\ {a\;sin\;x + b}&{ - \frac{\pi }{2} \le x < \frac{\pi }{2}}\\ {cos\;x}&{\frac{\pi }{2} \le x \le \pi } \end{array}} \right.\)Is continuous in [–π,π] then a = ________ and b = __________.
1
1, -1
2
1, 1
3
1, 2
4
-1, 1