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
행렬의 주대각선은 중요한 정보를 제공합니다.haengnyeol-ui judaegakseon-eun jungyohan jeongboreul jegonghamnida.The main diagonal of the matrix provides important information.