I have a really dumb question:
when calculating the area of a triangle <AOB, and AO = 2 and BO=2 and angle <AOB = 120 degrees, why can I not say the area is equal to 1/2*(2)*(2)?
You don't have the height of the triangle.
Even if you consider either of AO or BO as the base of the triangle the other is not the height, it is just the side of the triangle as the angle is 120 degrees.
A bend in the road is not the end of the road unless you fail to take a turn.....