How do you find the value of cot (-150)?

1 Answer
Oct 18, 2015

Cot (-150) = sqrt(3)

Explanation:

Cot(-150) = Cos(-150) / Sin(-150)
Now Cos (-x) = Cos (x) and Sin (-x) = -Sin (x)
Hence Cot(-150) = Cos (150) /(-sin(150))
= Cos(180 - 30) / (-Sin (180 - 30))
Also Cos (180 - x) = -Cos(x) and Sin (180 - x) = Sin (x)
So the expression becomes
-Cos (30) / (-Sin(30)
= Cos (30) / Sin (30)
Now Cos (30) = sqrt (3) / 2 and Sin (30) = 1/2
Hence Cos(30) / Sin(30) = sqrt (3) / 2 / 1 /2
= sqrt(3) / 2 * 2 = sqrt(3)