They brought the prototype out only once, late at night, to test it on the color projection television in one of the conference rooms.

这台机器只被他们带出过回，是某天的深夜，他们将它带到了议室，连接上彩色投影电视进行测试。

So to sum up, on the surface, the dot product is a very useful geometric tool for understanding projections and for testing whether or not vectors tend to point in the same direction.

综上所 面上 点积是个非常有用的几何工具用于理解投影和测试向量是否指向同个方向。