Ok, so we've been told that the angle H=68 degrees.
Let's now flip the right angled triangle 90 degrees clockwise.
If we do so, it turns out we'd have to find the opposite length of the right angled triangle (Opp) which is GI. We know that we have the adjacent (Adj) length of this triangle which is in fact 2cm. What we also know is that:
tan(β)=Opp/Adj *Whereby "β" is an angle.
As β=68 degrees, Opp=GI and Adj=2:
tan(68)=GI/2
Therefore:
GI = 2 * tan(68)
GI = 4.95 cm (to 2 decimal places)