Question

Evaluate: tan(-120 degrees).

Answer 1

-120° = -2π/3 radians.

Tangent is defined as Opposite/Adjacent or Sine/Cosine in a unit circle. So, if you have memorized the unit circle,

sin(-2π/3) = √3/2
cos(-2π/3) = -1/2

So, tan(-2π/3) would be:

`( ( √(3) )/(2) )/( (-1)/(2) ) = ( √(3) )/(2)* -(2)/(1)`

Simplify, and you get:

`-(2 √(3) )/(2) = - √(3)`

And, so, tan(-2π/3) = -√3