Объяснение:
а) cos60° + 2sin30° + 1/2*tg²60° - ctg 45° = 1/2 + 2*1/2 + 1/2*(√3)² - 1 = 1/2 + 1 + 1/(2*3) - 1 = 1/2 + 1/6 = 3/6+1/6=4/6=2/3
б) 3cos180° + 5ctg 270° - 2tg0 - sin 60° = 3*(-1) + 5*0 - 2*0 - √3/2 = -3 + 0 + 0 -√3/2=-3-√3/2
