Constructing a Parallelogram Using Input bar only
You can get even fancier. Construct a parallelogram by entering typing the following sequence of commands into the input box:
A = (1,1)
B = (4,5)
l = line[A,B]
C = (7,5)
m = line[C,l]
n = line[B,C]
o = line[A,n]
D = intersect[m,o]
polygon[A,B,C,D]
Additional commands you can use: ShowAxes[ <Boolean> ], ShowGrid[ <Boolean> ],