
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
OK. Post if you need to. I'll try to be more awake!!
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
Hey again,
I answered #11 wondering if it's correct
#11 I choose C 11. What is the measure of arc AC? A 54 deg B 137 deg C 180 deg D 111 deg E 174 deg F 23 deg
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
That makes sense. It must be a diameter.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
#12 I choose 4(D) because the hypotenuse is two times that of the leg opposite the 30 degree angle. The leg opposite the 30 degree angle is 60 degree angle and the question said AB is 4 So, I multiply 4 * 2=8 and the radius = 1/2 * 8 = 4 So that is my answer.
12. If ABC is a 306090 triangle, with angle ACB at 30 degrees, and line segment AC is the diameter of the circle, then if the length of line segment AB is 4, what is the radius of the circle?
A 8 B 2 C 10 D 4 E 7 F 16
#13 I choose A
13. Working with the information from 12 from here to #16, what is the measure of arc AB? A 90 deg B 25 deg C 30 deg D 120 deg E 60 deg F 72 deg
#14 F
14. What is the measure of arc BC? A 20 deg B 45 deg C 75 deg D 120 deg E 15 deg F 90 deg
15 E
15. Are arcs ABC and AC equal? A maybe Bnone of these Ckinda D55 E yes F no
I was wondering how I can find that ?
16. What is the measure of chord BC? A 6.928 B 2.098 C 5.281 D 10.112 E 9.475 F 7.461
Last edited by zeef (20121101 01:56:10)
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bobbym
 Administrator
Re: Circles: Chords, Radii, and Arcs
In mathematics, you don't understand things. You just get used to them. I have the result, but I do not yet know how to get it. All physicists, and a good many quite respectable mathematicians are contemptuous about proof.
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
hi zeef
12D is good for me too.
13F Don't think so. Just to check ... for an arc the measure is the angle it makes at the centre of the circle ??
14F Also here I get a different answer.
15E Yes
16 If Ois the centre of the circle, what are the angles in triangle OBC ?
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
13 The measure of an inscribed angle is equal to onehalf the degree measure of its intercepted arc.
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
hi zeef
The measure of an inscribed angle is equal to onehalf the degree measure of its intercepted arc.
That cannot be right. Look at these earlier answers:
#2 I choose B
2. If the measure of arc BFE is 80 degrees, then what is the measure of angle BME? A 37 deg B 80 deg C 9 deg D 23 deg E 17 deg F 41 deg
3. If there were an imaginary angle ACB, what would the measure of that angle be? (Hint: Remember that a line is an angle with a measure of 180 degrees, or that a circle has a total arc measure of 360 degrees.)
#4 I choose E
4. If angle EMA has a measure of 100 degrees, what is the measure of arc EDA? A 77 deg B 180 deg C 15 deg D 26 deg E 100 deg F 164 deg
In all these cases the 'measure of an arc' is the angle the arc makes at the centre of the circle.
I think you may be getting confused with something else.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
But weren't these talking about a central angle The measure of a central angle is equal to the length of the arc it defines. and we are talking about an inscribed angle now right ?
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
What do you mean by an inscribed angle?
Question 13 doesn't say anything about an inscribed angle.
#13 I choose A
13. Working with the information from 12 from here to #16, what is the measure of arc AB? A 90 deg B 25 deg C 30 deg D 120 deg E 60 deg F 72 deg
Let's take a step back from what the words mean and look at the diagram. I've reproduced it again below.
What are the following angles:
ACB = 30 ABC = BAC = AOB = ABO = OBC = BOC =
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
Acb = 30 Abc = 90 Bac = 60 Aob = 30 Abo = 90 Obc = 90 Boc = 60
Last edited by zeef (20121102 04:30:14)
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
So my answer would be the arc of AB= 30
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
14 E
14. What is the measure of arc BC? A 20 deg B45 deg C75 deg D120 deg E 15 deg F 90 deg
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
hi zeef
Do you have a compass and protractor? You might find it helpful to make your own accurate drawing.
(i) Draw a circle. (ii) Put on one diameter AC. (iii) Measure a 30 degree angle at C and find the point B on the circle. (iv) Check that ABC = 90.
Correct!
Correct, well done!
Correct, well done!
How did you get this? Look at triangle AOB. What sort of triangle is it?
This is also not correct. When you get AOB right, I think you'll find you can get this one right too.
The diagram is accurately drawn. Does this angle look like 90 ? Look at triangle BOC. What sort of triangle is it?
This answer will follow on from the answer to OBC
Now what about Q14 ?
I don't think this is answer E.
You should be giving the size of angle BOC here, so when you've got that right Q14 will be easy.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
It's an Acute Triangle so all the angles are less then 90.
Abo = 45 Obc = 45 Boc = 15
And when I add 45+15+30+45+15+30= 180 So that makes it correct.
Last edited by zeef (20121102 07:14:29)
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
14.I choose E 15°
14. What is the measure of arc BC? A 20 deg B 45 deg C 75 deg D 120 deg E 15 deg F 90 deg
15 I choose EYes
15. Are arcs ABC and AC equal? A maybe B none of these C kinda D 55 E yes F no
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
hi zeef
15 E yes. Correct!!
But you still haven't got 13 and 14 sorted out.
Did you try actually making a drawing.
Remember that A to O to C is a diameter and so also a straight line.
That means the angle CAB is the same as OAB. And you already know the measure of CAB.
And the triangle ABO has got three acute angles, true, but it's a bit more special than that.
Two of its sides are equal to the radius.
But don't say isosceles either.
Can you see that one of its angles is 60 degrees.
That makes it even more special.
Do you own a protractor? That's a plastic measuring device for angles. You can get semicircular ones and also full circle ones.
Picture below.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
Yes I own a protractor So that makes Ab= 60 bc= 75
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
We make progress. Arc AB is 60.
But BC is not 75.
See picture.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
Excellent!
So now let's recap all those answers.
ACB = 30 ABC = BAC = AOB = ABO = OBC = BOC =
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
Acb = 30 Abc = 90 Bac = 60 Aob = 30 Abo = 60 Obc = 120 Boc =60
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
Still not all correct.
Give me a moment to make a new picture.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
Acb = 30 tick Abc = 90 tick Bac = 60 tick Aob = 30 X Abo = 60 tick Obc = 120 X Boc =60 X
These last two look like you are measuring the wrong angles.
Bob
In my rush to make the pictures I've chopped off the text It should read "this is angle OBC, centre of protractor at B, measure angle between lines OB and BC"
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
 zeef
 Super Member
Re: Circles: Chords, Radii, and Arcs
Aob = 60 Obc = 30 Boc = 120
One, who adopts patience, will never be deprived of success though it may take a long time to reach him. Imam ali (as)<3
