Source: http://web.a9lame.com/Documents/Lyc%C3%A9e/Bac%20FR/c-2%C3%A9me%20Bac%20International/a-2%20Bac%20Sciences%20Math%C3%A9matiques%20A/b-Physique/a-Semestre%20I/b-Les%20ondes%20m%C3%A9caniques%20progressives/d-Exercices/Exercices%201%20Les%20ondes%20m%C3%A9caniques%20progressives.pdf