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#1 2012-12-16 03:16:10
- zee-f
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Geometry review
Hi,
I got C as an answer wondering if that is correct 
7. The apothem of a regular 9-sided figure is 6 feet and the area is 117.67 square feet. What is the perimeter of the regular 9-sided figure?
A 4.36 feet
B19.61 feet
C39.22 feet
D54.00 feet
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 2012-12-16 04:12:37
- anonimnystefy
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Re: Geometry review
C is correct. Good work!
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
#5 2012-12-16 05:12:13
- anonimnystefy
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Re: Geometry review
Hi
That is not correct.
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
#13 2012-12-16 10:24:31
- zee-f
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Re: Geometry review
Ok So can I cut the trapezoid into a square and a right triangle?
So the triangle side would be 8
10. In the diagram shown,line PN is parallel to line JQ , KN =16 centimeters, PN= 8 centimeters, and JQ = 14 centimeters. Determine the length of line NQ.
A 28 cm
B 12 cm
C 9.1 cm
D 7 cm
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#14 2012-12-16 10:28:21
- bob bundy
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Re: Geometry review
Triangle KJQ will have the same angles as KPN.
So it is an exact enlargement (do you say dilation?)
So you can use 8 ----> 14 to work out the scale factor
and apply to 16 ----> KQ
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#16 2012-12-16 10:52:49
- bob bundy
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Re: Geometry review
You don't need Pythag. It is simpler than that.
In my diagram, I've split away the larger triangle so you can see the enlargement effect more clearly (I hope).
So 8 gets enlarged to become 14. That's a scale factor of x 14/8
Apply the same scale factor to 16 and you will get KQ.
Youi'll still have to do a subtraction to get NQ
Bob
ps. You are not told there is a right angle so that's another reason for avoiding Pythag. I know it looks like 90 but it might not be.
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#17 2012-12-16 23:21:21
- zee-f
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Re: Geometry review
a bet confused because I don't remember taking dilation but
triangle KPN I get the following information :
opposite = 13.8564
hypotenuse = 16
adjacent = 8
and I get a 90 60 30 angle
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#18 2012-12-16 23:26:07
- bob bundy
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Re: Geometry review
hi zee-f
http://www.mathisfunforum.com/viewtopic.php?id=18566
post 6
Give me a moment and I'll come up with a better explanation for the latest problem.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#19 2012-12-16 23:52:10
- bob bundy
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Re: Geometry review
Right. One step at a time.
(i) Why you cannot use Pythagoras' theorem:- That angle that looks like 90 degrees may not be. The question doesn't say it is. Maybe it is 89 ?
And even if it is, working out KP doesn't get you any nearer to working out NQ.
(ii) This is a problem about enlargement, not Pythagoras. On the MIF teaching pages it is called 'Resizing'.
Have a look at
http://www.mathsisfun.com/geometry/resizing.html
I think you must have done it because it was on the transformations thread.
Have a look at both links and make sure you are clear about that.
(iii) I've taken your diagram and tried to show how the points J and Q are made by stretching the shape away from the centre at K.
P is stretched to J and N is stretched to Q.
A transformation like that is what I call an enlargement. But on your transformation thread the question said dilation, and bobbym used the same word, so maybe that's just the difference between UK english and USA english.
Whatever, my point is:- the triangle KPN has got bigger and the new bigger triangle is KJQ.
If it had got twice as big the scale factor would be x2. Three times as big would be x3.
In this problem it isn't as much as x2 because JQ is only 14 not 16.
So how can you work out the scale factor this time.
So
and then
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#23 2012-12-17 04:45:17
- zee-f
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Re: Geometry review
I choose B because Complementary angles are two angles whose measures total 90 degrees.
90 - 35 = 55 and it was incorrect.
1. Two angles are complementary. The smaller angle is 35° less than the larger angle. What is the measure of the larger angle?
A- 27.5°
B- 55°
C- 62.2°
D- 125°
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
#24 2012-12-17 05:47:50
- bob bundy
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Re: Geometry review
hi zee-f
NQ = 12 is what I what I got too.
Complementary angles add up to 90
The question doesn't say "Two angles are complementary. The smaller angle is 35°. What is the measure of the larger angle?
It says "Two angles are complementary. The smaller angle is 35° less than the larger angle. What is the measure of the larger angle?
Do you see the difference?
So if the larger one is x the smaller one is (x-35) and together they add up to 90.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei