Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
활공역학은 비행기의 성능을 이해하는 데 중요하다.hwal-gong-yeok-hak-eun bihaeng-gi-ui seongneung-eul ihaehaneun de jung-yohada.Aerodynamics is important for understanding the performance of an aircraft.