Here the length of the given side is 8, with an angle of 45 at either end (to start with). The angles can be changed by moving D and E. Move D around, then E. Notice what happens ... What is the size of the angle at C? Move A and B so that AB is horizontal. Adjust D and E to suit. As you explore, notice which angles are acute, which are obtuse ... are there any right angles? Write down everything your notice ...