Television, films and books give us ideas about what British people are like Which of these characteristics comes into your mind when you think of the British?

Угол лежит в 1 четверти, там косинус положительный. по формуле двойного угла для косинуса находим:
cosα = cos(2*α/2) = 2cos^2(α/2) - 1 = 7/18
2cos^2(α/2) = 25/18
cos^2(α/2) = 25/18
cos(α/2) = √(25/36) = 5/6
6cos(α/2) = 5