Question

Is anybody good with Proofs!? Will give medal!

Answer 1

What is the assumption needed to begin an indirect proof of the following statement?

“Cows do not have horns.”

Bulls do not have horns.

Bulls have horns.

Cows do not have horns.

Cows have horns.

Answer 2

in indirect proof, you always start by assuming the opposite of the thing u wanto prove

Answer 3

so it would be D?

Answer 4

yes !

Answer 5

yes thats correct

Answer 6

Thank you, can you help me with another?

Answer 7

sure ask

Answer 8

thanks @blossomemerald

Answer 9

okay!

Answer 10

Heather is doing an indirect proof with five given statements and one conclusion. How many of these statements can be true based on her assumption to contradict the assumption and prove the original conclusion?

At most four

All five

Exactly three

At least one

would it be A?

Answer 11

or is it D? I really don't understand what they are asking

Answer 12

yes ! you're awesome with proofs !! at least one contradiction is sufficient to conclude

Answer 13

oh you said u dont understand what they asking lol but you got the answer right. its D

Answer 14

heres the thing :- in indirect proof, we start wid assuming the opposite of what we need to prove is true. and look for atleast one contradiction of given statements or premesis. if we get a contradiction, we're done wid proof.

Answer 15

oh okay(:

Answer 16

you got more qs

Answer 17

Angie did the following proof in her logic class. Which step in the indirect proof did she do incorrectly?

Prove: 8 is divisible by 4.

Step 1: Assume that 8 is not divisible by four.
Step 2: 8 is divisible by 4
Step 3: 8 is divisible by 4.

Step 1

Steps 1 and 3

Step 3

Step 2

Answer 18

so then that one would be C?

Answer 19

why

Answer 20

is that right?

Answer 21

she started right - by assuming the opposite is true. so step1 is right

Answer 22

so it must be C or D
gimme a sec to think

Answer 23

i would tick D. cuz step 1 and step 3 are perfect !

Answer 24

well you said that we start by assuming the opposite of what we need to prove is true. and look for at least one contradiction of given statements..so saying that 8 is divisible by 4 would end the proof because that is correct, there is no need for a 3rd step..i think lol

Answer 25

also steps 2 & 3 say the same thing, you wouldn't need to list it twice. would you?

Answer 26

lol i see your point wait let me think again

Answer 27

step1 and step3 are a must in indirect proof

Answer 28

in step2 only we need to show something that contradicts.

step2 has to be something like :-

step2 : 8 = 4*2

or

step2 : 4 is a factor of 8

Answer 29

at step2, you cannot conclude.

Answer 30

tick D, you will come to knw whe u submit anyways :)

Answer 31

this is so confusing but okay, if you say so lol

Answer 32

ok. indirect proof template is like that, you must have 3 steps.

Answer 33

ohhhhh nvm I get what you r saying now, there would have to be something else there for step 2 so that you can prove 8 is divisible by 4. I am no longer confused lol

Answer 34

1. assumption
2. contradiction
3. conclision

Answer 35

yes :)

Answer 36

yayyy! haha. okay but I have one more lol

Answer 37

Shelly, Jess, and Andrea are all working at an amusement park for the summer. The manager finds out that one of them left the key in the door to the security office. When he asked them who did it, they replied:

Shelly: Andrea did it.
Jess: Shelly did not do it.
Andrea: I didn’t do it.

The manager believed Andrea. Use an indirect proof to show that Andrea did not leave the key in the security office door.

Hint: Begin by assuming Andrea did leave the key in the door.

Answer 38

openstudy is always losing connection -___________________-

Answer 39

I know-
Step 1: Assume Andrea did leave the key in the door.
Step 2: ?

Answer 40

Since we need to prove "Andrea did not leave the key in the security office door", we begin by assuming the opposite of it, that Andrea did leave the key in the door.

Shelly says, Andrea did it. which is fine with our assumption that Andrea did it.

Jess says, Shelly did not do it. which is fine with our assumption that Andrea did it.

Andrea says, Andrea did not do it. which is a CONTRADICTION to our assumption that Andrea did it.

since atleast one of the statements is contradicting with our assumption that Andrea did it, our assumption must be false. So Andrea did not do it.

Answer 41

you can put them in 3 steps

Answer 42

ohhh, how can it be that easy nd Andrea could be lying!

Answer 43

Step 1 :
Since we need to prove "Andrea did not leave the key in the security office door", we begin by assuming the opposite of it, that Andrea did leave the key in the door.

Step 2:
Shelly says, Andrea did it. which is fine with our assumption that Andrea did it.

Jess says, Shelly did not do it. which is fine with our assumption that Andrea did it.

Andrea says, Andrea did not do it. which is a CONTRADICTION to our assumption that Andrea did it.

Step 3:
since atleast one of the statements is contradicting with our assumption that Andrea did it, our assumption must be false. So Andrea did not do it.

Answer 44

we dont care whether Andrea is lying or not. All we care is whether we got a contradiction or not.

Answer 45

lol okay so it would be...
Step 1: Assume Andrea did leave the key in the door.
Step 2: Shelly says, Andrea did it
Step 3: Jess says, Shelly did not do it
Step 4: Andrea says, Andrea did not do it

Answer 46

not so many steps. compress it in only 3 steps

Answer 47

Heather is doing an indirect proof with five given statements and one conclusion. How many of these statements can be true based on her assumption to contradict the assumption and prove the original conclusion?

At most four

All five

Exactly three

At least one

^^^ I got this question wrong^^^

Answer 48

hey this is the q for which i said answer is "atleast one"

Answer 49

huh.. i see its wrong.

Answer 50

answer is All five

Answer 51

:/ oh

Answer 52

i misread the question as :- "How many of these statements can be\( \color{red}{\cancel{true} \ false}\ \)based on her assumption to contradict the assumption and prove the original conclusion? "

Answer 53

but my explanation for that q holds good :-

heres the thing :- in indirect proof, we start wid assuming the opposite of what we need to prove is true. and look for atleast one contradiction of given statements or premesis. if we get a contradiction, we're done wid proof.

Answer 54

its okay...im not worried about it nd thank you so much for all your help...if I could give you 5 medals I would but I cant lol .-.

Answer 55

lol ty :) you have more qs

Answer 56

yes but for some reason my computer isn't letting me see the pictures of the angles

Answer 57

thats weird ! these are from connexus or flvs ?

Answer 58

flvs

Answer 59

ohk, to my experience, flvs works well with internet explorer. it bugs sometimes in in chrome/firefox

Answer 60

yea I am on internet explorer

Answer 61

do you have any other questions

Answer 62

this is what I am seeing

Answer 63

yes the one that I just posted n the attachment that isn't letting me see the images, I don't know if you can understand it

Answer 64

no pics - no sense :|

Answer 65

fuh real lol

Answer 66

you're in mid of assessment or you can close and reopen

Answer 67

I can close it and reopen

Answer 68

@ganeshie8

Answer 69

good :) it may work.. try it

Answer 70

nopee its still not showing it .-.

Answer 71

uhh.. call the instructor

Answer 72

I got it!

Answer 73

ah finally some pics lol, whats the q btw

Answer 74

Use a paragraph proof to prove the corresponding angles postulate:

Given: segment AB ∥ segment CD
Prove: Corresponding angles are congruent

Answer 75

any ideas?

Answer 76

yes we use alternate interior angles theorem

Answer 77

what is the definition of that ?

Answer 78

when two parallel lines are cut by a transversal, the resulting alternate interior angles are congruent. is that it?

Answer 79

Sine line segment AB is parallel to the line segment CD, \(\angle 4 \cong \angle 6\) by alternate interior angles theorem. And since \(\angle 4\) and \(\angle 2\) are vertical angles, they must be congruent by vertical angles theorem. So \(\angle 4 \cong \angle 2\). By substitiution, \(\angle 2 \cong \angle 6\). Hence the corresponding angles are congruent.

Answer 80

yes, go thru above paragraph proof and see if it makes some sense

Answer 81

doesn't the equal sign with a curvy line mean approximately equal too?

Answer 82

@ganeshie8

Answer 83

NO

Answer 84

in geometry it means congruent.

Answer 85

congruent means, exactly equal to