Question

Вычислите cos45° * sin3105° + 1/2ctg(-318°)-cos270°

Answer 1

Cos45° * Sin3105° + 1/2ctg(- 315°) - Cos270° = Cos45° * Sin(360° * 8 + 225°) -
- 1/2ctg(90° *2 + 135°) - Cos270°= Cos45° * Sin225° - 1/2ctg(90°+45°) - Cos270° =
= Cos45° * Sin(180° + 45°) + 1/2tg45° - Cos270° = - Cos45° * Sin45° +
+ 1/2 tg45° - Cos270° = - √2/2 * √2/2 + 1/2 * 1 - 0 = - 1/2 + 1/2 = 0