Question

Geometry Proofs
Someone please please help me.
I've done some of the questions, but don't know if they're right.
@phi @thomaster

Answer 1

Can someone please help me? I'm really desperate

Answer 2

For the first question you posted, what is the reason
statement (b) is true?
why can you say AC= AC ?
see a list of reasons that might apply: http://www.regentsprep.org/Regents/math/geometry/GPB/theorems.htm

can you try?

Answer 3

They're both the same question.

Answer 4

@phi

Answer 5

look at the second attachment

Answer 6

ok, so you only need the reason for statement ( c ) ?

Answer 7

Yes, and can you check out the rest of my answers. Please, I'm not really good at these questions

Answer 8

A statement is true because either
(1) It is assumed to be true. i.e. given as true, or
(2) There is a theorem or property that makes it true.

I would first test reason (1) (check what is given)
then I would check the list of theorems to see if any apply.

Answer 9

it is true

Answer 10

what is the reason it is true ?

Answer 11

they're congruent

Answer 12

what reason should you give for statement c) ?

Answer 13

I honestly don't know...

Answer 14

why can you say
\[ BA \perp AC \] ?

Answer 15

they're perpendicular?

Answer 16

\( BA \perp AC\) is just a way to say they are perpendicular.

What we want is a reason to believe they are perpendicular. Read this carefully:
A statement is true because either
(1) It is assumed to be true. i.e. given as true, or
(2) There is a theorem or property that makes it true.

Answer 17

In a proof, we start with some things that are assumed to be true. (we say they are given)

I would always check the list of givens. If a statement is on the list of givens, then we know why we say it is true. It is because it is Given.

Answer 18

so it is true?

Answer 19

all the statements in the proof are true and it is a valid proof.

what you are doing is writing down a *reason* why each statement is true.

for statement c) what is the reason?

Answer 20

one of the "easy" reasons a statement is true, is because we start the proof with a list of statements that we assume are true. we list them in the section labeled Given.

Answer 21

I'm sorry but I don't know, I'm so confused ):

Answer 22

In your proof, do you see the list of Givens ?

Answer 23

yeah

Answer 24

and what is on that list ?

Answer 25

wait you mean on the question?
I'm sorry I'm confused

Answer 26

Yes, on the question, at the top,they give a list labeled Given
what is on that list ?

Answer 27

AB = CD
BA is perpendicular to AC
DC is perpendicular to AC

Answer 28

do you see what reason to say
statement c) is true ?

Answer 29

No, I don't ):

Answer 30

statement c) says
BA is perpendicular to AC
DC is perpendicular to AC

those are on the list of Given

Answer 31

so i put given?

Answer 32

the same reason statement a) is true

Answer 33

yes, if a statement is Given, it is true by assumption.

Answer 34

thank you!!
Can you see if the others are right please

Answer 35

if you don't mind

Answer 36

the rest look ok

Answer 37

Thank you so so much

Answer 38

except statement (g)

Answer 39

ok, so how do i do it?

Answer 40

There are only a few reasons why you can say one triangle is congruent to another triangle.
the reasons are listed on the link posted above
http://www.regentsprep.org/Regents/math/geometry/GPB/theorems.htm

Answer 41

The first reason on the list is
SSS
short for side-side-side

do the statements show all 3 sides of the first triangle are congruent to the 3 sides of the other ?

Answer 42

yes

Answer 43

statement (a) shows one side of the 3 sides is congruent
statement (b) shows another side of the 3 sides is congruent
but you won't find any other that shows the third sides are congruent.

Answer 44

so it's no then?

Answer 45

you can't use SSS (we have only 2 out of the 3 sides)

try the next reason
SAS
short for side-angle-side
in that order.
you need a statement that shows 2 sides and the angle between the two sides
match up (are congruent) between the 2 triangles.

Answer 46

we have two sides and an angle

Answer 47

yes. and the angle (the right angle) is in between the two sides (we can't use just *any* angle, it has to be the angle between the two sides)

so the reason for statement (g) is SAS

Answer 48

and the others are good, right?

Answer 49

yes

Answer 50

thank you so so much i deeply appreciate it

Answer 51

proofs are confusing. It takes work to understand them.

Answer 52

if you have time, watch how they are done
http://www.khanacademy.org/math/geometry/geometry-worked-examples/v/ca-geometry--more-proofs

Answer 53

i will later today, thanks again