# 739. 10 sides b:ааregular decagon 740. If the diagonals ```7&shy;39. 10 sides
b: regular decagon
7&shy;40. If the diagonals intersect at E, then BE = 12 mm, since the diagonals are perpendicular bisectors. Then ΔABE is a right triangle and
AE = √152 &shy; 122 = 9 mm. Thus, AC = 18 mm.
7&shy;41. Yes, she is correct. One way: Show that the lengths on both sides of the midpoint are equal and that (2, 4) lies on the line that connects (&shy;3, 5) and
(7, 3) .
7&shy;42. (a) and (c) are correct because if the triangles are congruent, then corresponding parts are congruent. Since alternate interior angles are congruent, then AB // DE .
7&shy;43. AB = √40 ≈ 6.32, BC = √34 ≈ 5.83, therefore C is closer to B.
1
Warm up
Write down the method and meanings on page 346 and write the definition down of a regular polygon on page 351
2
3
7 &shy; 43
A
C
B
4
Lesson 7.2.1 What can congruent triangles tell me?
Objective: students will be introduced to proofs and will learn more properties
of parallelograms and kites
NOTE: first semester we studied triangles, now we are going to switch to QUADRILATERALS
In&shy;class
7&shy;44 learning properties about parallelograms
Part d) make a flowchart for showing that the two triangles are congruent
VERY IMPORTANT THAT YOU UNDERSTAND THIS
LEAVE ROOM ABOVE YOUR FLOWCHART TO ADD THINGS
7&shy;45 There are a few things we need to add, once most groups are done I will
go over this with the whole class
7&shy;46 Let's look at a KITE
7&shy;47 looking at the other diagonal of a kite and using it to make a congruency flowchart
7&shy;48 write down the properties you learned about parallelograms and kites
today
A
B
7&shy;44
D
C
5
7&shy;45
AB // CD
Given
If lines are //, then
alternate interior angles
are ≅
Given
&lt;ABD ≅ &lt;CDB
BD ≅ BD
Reflexive property
If lines are //, then
alternate interior angles
are ≅
ASA ≅
6
C
7 &shy; 47
A
AC ≅ BC
C
B
A
D
B
CD ≅ CD