Variational principles play an important role in the formulation of many problems of mathematical physics.变分原理现在许多数学物理的表述中起着重要作用.After studying differential calculus you will be able to solve these mathematical problems....
Pete got on his horse and started trotting across the field.皮特跨上马，开始在田野间小跑起来。The riders came trotting down the lane.这骑手骑着马在小路上慢跑.Alan took the reins and the small horse started trotting.艾伦抓住缰绳，小马开始慢跑起来。...
Pain-killers are very useful in small amounts to bring your temperature down.小剂量的止痛药对于降低体温非常有用。The police are searching for his killers.警方正在搜捕杀害他的凶手。Giant-killers Yeovil became the most successful non-league club in hist...