三棱柱ABC-A1B1C1中,AB=AC,且侧面A1ABB1与侧面A1ACC1的面积相等,则∠BB1C1等于[ ]
A.45°
B.60°
C.90°
D.120°
答案:C
若a+b=﹣3,ab=2,则a2+b2=﹙ ﹚.