Name: An
Student
Level: secondary
Hi, Im taking a geometry course for the summer , and we just started
to learn about proofs for about one week. Today in class, we started
to do this one proof but didnt finish it because class ended. the problem
is as follows.
NOT DRAWN TO SCALE
This is what i have so far
Statements Reasons
1. ABCD is a Parallelogram a)
given
AC is congruent to BD
2. AD is congruent to BC b)
definition of parallelpgram
AB is congruent to DC
3. BD is congruent to BD c)
reflexive property
4. triangle ABD is conruent to triangle CDB d)
SideSideSide Theorem
As a class, we formulated a plan. In order to show that the parallelogram is
a rectangle, we have to prove that the all the
angles are 90 degreees. This is what i need help on. How do you finish this
proof, and how do you prove that an angle is 90 degrees?


Hi An,
This is good so far.
Using the same argument you can prove that triangles ABC and CDA are
congruent. Then, since AC and BD are congruent you can prove that triangles
ABC and ABD are congruent. Hence triangles ABC, CDA, ABD and DBC are
all congruent.
Can you see how to complete the proof?
Penny

