— What colour is it?
— _____________.
(1)5-3+25+3-2 (2)25420-345+25
如图所示,两根等长的轻绳将日光灯悬挂在天花板上,两绳与竖直方向的夹角都为450,日光灯保持水平,所受重力为G,左右两绳的拉力大小分别为()