Ответы: 1
Михаил Вышневецький
2017-11-15 15:10
Tg^2 f + sin^2 f — 1/cos^2 f = sin^2 f/cos^2 f + sin^2 f — 1/cos^2 f = sin^2 f/cos^2 f — 1/cos^2 f + sin^2 f = (sin^2 f — 1)/cos^2 f + sin^2 f = (sin^2 f — sin^2 f — cos^2 f)/cos^2 f + sin^2 f = — cos^2 f/cos^2 f + sin^2 f = -1 + sin^2 f = -cos^2 f — sin^2 f + sin^2 f = -cos^2 f