Thanks, EP
The last one might be a little difficult
-7pi/ 12 x 180 / pi = (-7/12)* 180 = -105° = 360 - 105 = 255°
And 255° = 210° + 45°
So
tan ( 255°) = tan ( 210° + 45°) =
tan (210) + tan (45) 1/√3 + 1 [ √3 + 1 ] / √3
_________________ = _______________ = ______________ =
1 - tan (210)tan(45) 1 - (1/√3)(1) 1 - 1/√3
[ √3 + 1 ] / √3 [ √3 + 1 ] 4 + 2√3
________________ = ____________ = ________ = 2 + √3
[ √3 - 1 ] / √3 [ √3 - 1 ] 3 - 1