a.cos 150°+cot(-330) b.cosec 450°-2 sin 270°

a.
cos (180-30) + (-cot (270+60))
= -cos 30 - (-tan60)
= -1/2 akar 3 + akar 3
= 1/2 akar 3

b.
cosec450 - 2sin270
= cosec (360+90) - 2 sin (270-0)
= cosec 90 - 2(-cos 0)
= 1 + 2
= 3