It means find the angle whose tangent equals - sqrt (3) the negative square root of 3 =
(-<span>
<span>
<span>
1.7320508076)
</span>
Looking up the arc tan </span></span><span>(-1.7320508076</span> ) on this page: http://www.1728.org/trigcalc.htm we find it equals -60 degrees
