[填空题]
What is the linear speed6fvtf /ylpjgl)g +k3 7 o7 rl58b*soe :sx1+l w /mwoctmf 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? $m/s$