The agreement to be signed Thursday replaces the START-1 treaty, which U.S.President George H.W.Bush and Soviet President Mikhail Gorbachev signed in 1991.

VOA: standard.2010.04.04

For example, if t* is the time you hit the ground, then t* satisfies the equation h - 1/2 g ^2 = 0.

例如,如果在 t* 时刻落地,那 t* 就满足等式 h - 1/2 g ? ^2 = 0

耶鲁公开课 - 基础物理课程节选