1) 3tg (-пи/6) * ctg (пи/3) + sin (3 пи/2) - 4cos (пи/4)

2) cos240 градусов+ctg225 градусов

3) сos (a-b), sin a=-5/13, cos b=-12/12, Пи

1

3 * (-√3/3) * √3/3 + (-1) - 4*√2/2=-1-1-2√2=-2-2√2

2

сos (270-30) + ctg (180+45) = - sin30+ctg45=-1/2+1=1/2

3

cosa=-√ (1-sin²a) = - √ (1-25/169) = - √ (144/169) = - 12/13

sinb=-√ (1-cos²b) = - √ (1-1) = 0

cos (a-b) = cosacosb+sinasinb=-12/13 * (-12/13) + (-5/13) * 0=144/169+0=144/169