Задача 4893 Найдите -13cos2a, если sina=-0,1...

slava191

31.10.2015

Найдите -13cos2a, если sina=-0,1

cos2a = cos^2a-sin^2a = 1-2sin^2a = 1 - 2*(-0.1)^2 = 1 - 2*0.01 = 0.98

-13cos2a = -13*0.98 = -12,74

Ответ: -12,74

vk121561309

29.01.2017

cos2a = cos2a–sin2a = 1–2sin2a = 1 – 2·(–0.1)2 = 1 – 2·0.01 = 0.98

–13cos2a = –13·0.98 = –12,74