Until the eighteenth century, people relied on energy derived from plants as well as animal and human muscle to provide power.
直到18世纪，人们还依赖于来自植物、动物和人类肌肉的能量来为自身提供动力。
2
Tests are derived primarily from requirements, but they draw from other sources as well.
测试最初源于需求，但它们也源于其他来源。
3
Kepler's Third Law, which you derived on your exam as well as on an assignment: r1 the period squared equals four pi squared times r1 plus r2 to the power three.