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GeoGebraLección de GeoGebra

Coordinate Proof of Isosceles Trapezoid Diagonals

Investigate how positioning an isosceles trapezoid symmetrically on the coordinate plane leads to a general proof that its diagonals are congruent.

Tarea 1

Putting It All Together

Answer these open ended questions on your own or with others to form deeper math connections.

Tarea 2

How can we be sure the general algebraic proof holds for all trapezoids?

Tarea 3

Why is it helpful to rotate and translate the trapezoid before attempting a general algebraic proof that the diagonals are congruent?

Tarea 4

How could you show algebraically that the diagonals of a rectangle are congruent?

Tarea 5

John claims that if you take the midpoints of all the sides of any isosceles trapezoid and join them together, the resulting figure will be a parallelogram. What steps would he need to take to prove this claim using algebra? How could you prove it using geometry?