求指导本题解题过程，谢谢您！36.已知 overrightarrow (a)cdot overrightarrow (b)=3, overrightarrow (a)times overrightarrow (b)= 1,1,1 , 求 langle overrightarrow (a),overrightarrow (b)rangle = __

求指导本题解题过程，谢谢您！