Дано: cos a = 1/3
tg a = sqrt(1 - (cos a)^2) = sqrt(1 - (1/3)^2) = sqrt(1 - 1/9) = sqrt(8/9) = 2sqrt(2)/3
7,4 - tg^2a = 7,4 - (2sqrt(2)/3)^2 = 7,4 - (4*2)/9 = 7,4 - 8/9 = 66,6/9 - 8/9 = 58,6/9
Ответ: 58,6/9
Дано: cos a = 1/3
tg a = sqrt(1 - (cos a)^2) = sqrt(1 - (1/3)^2) = sqrt(1 - 1/9) = sqrt(8/9) = 2sqrt(2)/3
7,4 - tg^2a = 7,4 - (2sqrt(2)/3)^2 = 7,4 - (4*2)/9 = 7,4 - 8/9 = 66,6/9 - 8/9 = 58,6/9
Ответ: 58,6/9