Two opposite sides of a parallelogram each have a length of #9 #. If one corner of the parallelogram has an angle of #(2 pi)/3 # and the parallelogram's area is #18 #, how long are the other two sides?
If the whole area is made of two equal triangles, and has an area of 18 in total, then the area of one triangle is
Area of a triangle
In this case,