Aim #12: How do we apply the properties of quadrilaterals in coordinate
geometry proofs (day 3)?
1) Quadrilateral ABCD has vertices A(-3,-2), B(9,2), C(1,6) and D(-5,4).
Prove that ABCD is a trapezoid.
2) Quadrilateral ABCD has vertices A(-8,2), B(0,6), C(8,0) and D(-8,-8).
Prove that ABCD is an isosceles trapezoid.
3) On the set of axes below, graph and label ∆DEF with vertices at D(-4,-4), E(,2,2) and F(8,-2).
If G is the midpoint of EF and H is the midpoint of DF, state the coordinates of G and H and
label each point on your graph. Explain why GH || DE.
4) The vertices of ΔGHI are G(1,1), H(5,3) and I(4,5). Prove that ΔGHI is a right
triangle. State the coordinates of point J such that quadrilateral GHIJ is a
rectangle. Prove that GHIJ is a rectangle.