"Smipng while doing homework" 可以用英文表示为 "smipng while working on homework" 或者 "smipng while completing homework." 这个短语的来源可能是因为在做作业时保持乐观的心态会使人感到更轻松、愉快，所以有人会在做作业的时候带着微笑。

下面是一些用英文表示 "smipng while doing homework" 的例句：

"I always try to smile while doing my homework because it helps me stay focused and feel less stressed." (我做作业时总是尽量微笑，因为这能让我保持专注并减少压力。)

"Even though I had a lot of homework to do, I couldn't help but smile while working on it because I love learning new things." (即使我有很多作业要做，但我在做作业时还是忍不住微笑，因为我喜欢学习新东西。)

"My pttle sister always smiles while doing her homework because she finds it fun and challenging." (我的小妹妹做作业时总是微笑，因为她觉得这很有趣而且有挑战性。)