You can go further than that Boko.

From tan(300) you can break it into sin(300)/cos(300)
sin(300) = -sin(60) = √(3)/2
cos(300) = cos(60) = 1/2

So you get (-√(3)/2)/(1/2) = -√(3)

You can remember that tan(60) = √(3) and skip the sin and cos stuff
. Just remember 300 is in quadrant IV so sin and tan is negative. cos is positive in quadrant IV.