[填空题]
What is the linear spep0n 9 dlozqh+3 ll6+t jg-+kt7 l /4o:ddp lfqes il9tc0k7t.eed of a point (a) on the equator, $m/s$ (b) on the Arctic Circle (latitude 66.5$^{\circ} $ N), $m/s$ (c) at a latitude of 45.0$^{\circ} $ N, due to the Earth’s rotation? $m/s$