# Help with trapezoid proof please!

• May 7th 2010, 11:42 AM
Given: LORI is a rectangle; seg LB cong seg DO
Prove: BIRD is an isosceles trapezoid
__________________________________________________ _________________
Statements *Reasons

LORI is a rectangle; seg LB cong seg DO
*Given
__________________________________________________ _________________
• May 7th 2010, 12:04 PM
masters
Quote:

Given: LORI is a rectangle; seg LB cong seg DO
Prove: BIRD is an isosceles trapezoid
__________________________________________________ _________________
Statements *Reasons

LORI is a rectangle
*Given
__________________________________________________ _________________

Here we go....

$\displaystyle \overline{LB} \cong \overline{DO}$
GIVEN

LORI is a rectangle.
GIVEN

$\displaystyle \angle L$ and $\displaystyle \angle O$ are right angles.
A RECTANGLE HAS 4 RIGHT ANGLES.

$\displaystyle \triangle BLI \:\:and\:\:\triangle DOR$ are right triangles.
DEFINITION OF RIGHT TRIANGLE

$\displaystyle \overline{LI} \cong \overline{OR}$
OPPOSITE SIDES OF A RECTANGLE ARE CONGRUENT

$\displaystyle \triangle BLI \cong \triangle DOR$
LL Theorem

$\displaystyle \overline{BI} \cong \overline{DR}$
CPCTC

BIRD is a trapezoid.
DEFINITION OF ISOSCELES TRAPEZOID
• May 7th 2010, 12:11 PM
What is the LL theorem? oh and I think you mean triangle BLI not BLO :D
• May 7th 2010, 12:15 PM
masters
Quote:

What is the LL theorem?

LL Theorem: Congruency theorem for right triangles only.

If the legs of one right triangle are congruent to the
corresponding legs of another right triangle,
then the triangles are congruent.

This theorem is proved using the SAS postulate.
• May 7th 2010, 12:24 PM