1.cos 120 derajat 2. Sin 135 derajat 3. Cot 210 derajat 4. Cos (-390 derajat)

1.
cos (90+30)
= -sin 30
= -1/2

2.
sin (90+45)
= sin 45
= 1/2 akar 2

3.
cot (180 +30)
= cot 30
= akar 3

4.
cos (-390)
= cos 390
= cos (360+30)
= cos 30
= 1/2 akar 3