The arches were made as early as the 2nd millennium BC in Mesopotamian back agriculture, and their systematic use started with the ancient romans who were the first to apply the technique to a wide range or structures.
The Purpose was to give it more strength, although it had limited the size and scope of the building. As a result, builders couldn't construct extremely large structures.
Answer: Motet is usually a more religious work with larger groups of musicians , while Madrigal stays as a small unit/smaller group of musician. Motet is known to be more on the religious side, and Madrigal is "less religious." The Madrigal was known to died out when the Baroque period had started, while Motet was still thriving.