Hi, I would express each point of the triangle as as an (x,y) coordinate, then express each ordinate of each point as the desired function of time, i.e. x(t) or y(t), so that each coordinate is 'parameterised' by time. Then you can express things like internal or external angles, or triangle area based on the location of the the coordinates using things like the sine rule and the cosine rule. Is that any clearer? what are you trying to do exactly?