Question

How to find the value of `cot -216^@`?

Answer 1

On the trig unit circle,

`cot (-216) = cot (360 - 216) = cot 144 = cot (180 - 36) = -cot 36`

Calculator gives tan (36) = 0.73 -> `cot (36)= 1/0.73 = 1.37`

`cot(-216) = -1.37`