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#1 2012-12-12 23:06:57
- zee-f
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Proof
Hi,
I really need help seeing if I answered the following correct:
I'll give you an assumption, and ask you to provide proof for the assumption. If there is no proof for the assumption, the answer is "unfounded."
I choose A
1. If I have two coplanar lines, I must have a plane.
A-unfounded
B-Definition of a point
C-Definition of a plane
D-Given
E -Definition of a line
F -Definition of radius
Last edited by zee-f (2012-12-12 23:41:33)
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#2 2012-12-13 03:43:32
- bob bundy
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Re: Proof
hi zee-f,
I think this can be proved. Isn't a plane defined by 3 (non-colinear ) points?
How could you find 3 such points on those two lines?
But I don't understand how you can prove that with just a letter. Have you got any examples of this sort of thing?
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#3 2012-12-13 04:54:47
- anonimnystefy
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Re: Proof
A is correct.
The statement isn't even true. Two lines that are actually the same line do not define a single plane, but are coplanar.
The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“A secret's worth depends on the people from whom it must be kept.” ― Carlos Ruiz Zafón
#4 2012-12-13 05:02:55
- zee-f
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Re: Proof
I answered A and it was incorrect 
.
Yeah this lesson is confusing but I did answer 14 correctly like this one :
(F ) was correct
6. In the figure above, line segment MC is equal to imaginary line segment MI.
A Given
Bunfounded
CDefinition of supplementary angles
D1267200 inches
E Definition of an octagon
F Definition of a circle: all points are equidistant from the center
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#6 2012-12-13 05:47:20
- bob bundy
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Re: Proof
stefy wrote:
Two lines that are actually the same line do not define a single plane, but are coplanar.
I did consider this, but rejected this interpretation on the grounds that 'two lines' should mean exactly two distinct lines not one line counted twice.
That's the trouble with using English to make mathematical statements. It sometimes isn't precise enough.
As zee-f has had A marked wrong, I think we have further evidence that the questioner was thinking that way too.
So let's assume the lines are either (i) distinct and parallel or (ii) they cross at a point
So we either have 4 distinct points or at least 3.
What do we need to define a plane?
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#7 2012-12-13 06:29:35
- zee-f
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Re: Proof
Hi,
According to my online courses A plane is defined by any of the following:
three points not lying on a line
a line and a point not lying on the line
two lines which intersect in a single point or are parallel
So I think C would be a correct answer
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#9 2012-12-13 08:30:23
- zee-f
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Re: Proof
I am still confused on what am really doing 
I got 6 incorrect out of 20 
I choose A and it was incorrect 
7. In the figure above, line segment EJ is equal to line segment JM
A Definition of radius
Bunfounded
CDefinition of an octagon
D1267200 inches
E Given
F Definition of supplementary angles
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#10 2012-12-13 08:43:58
- bob bundy
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Re: Proof
6/20 eeekkk!
Oh hang on. 6 wrong. 
Oh that's not so bad. 70% is a good score.
But we'll get them sorted. Don't worry.
I need to see the diagram for this one.
bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#12 2012-12-13 19:25:12
- bob bundy
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Re: Proof
hi zee-f,
Oh, that diagram. I remember that from another set of questions.
So EJ = JM ? They're not telling that; they're asking is it true?
Take a look at the diagram. Is J half way along EM ?
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#16 2012-12-14 06:10:51
- zee-f
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Re: Proof
I choose E and it was incorrect
my new answer is D
14. If a central angle is 30 degrees, then the arc it defines is also 30 degrees.
A Given
BDefinition of an inscribed angle
Cunfounded
DProperties of a central angle
E Properties of an arc
F Definition of radius
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#19 2012-12-14 06:34:26
- zee-f
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Re: Proof
E was incorrect I still don't see why O_o
16. If a radius bisects a chord, then the lengths of the parts of the radius on either side of the chord are equal.
A Given
BDefinition of a chord
Cunfounded
DDefinition of supplementary angles
E Definition of a bisector
F Definition of radius
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#23 2012-12-14 10:16:00
- zee-f
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Re: Proof
2 more left 
I answered C for both it was incorrect
19. The given points (4, -8), (4, -5), and (-2, -6) make a right triangle.
A Distance Formula
B Definition of a right triangle
CDefinition of a triangle
Dunfounded
E Pythagorean Theorem
F Definition of radius
20. The given points (2, -3), (-7, -7), (2, -7), and (-7, -2) make a square.
A Definition of coordinate
BPythagorean Theorem
CDefinition of a square
DDefinition of supplementary angles
E Distance Formula
F unfounded
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3