
 bob bundy
 Moderator
Re: Circles: Chords, Radii, and Arcs
You've made up 60 and 30 because that's what those angles look like. But remember D could be anywhere on the circumference.
I've added a few more possibilities in different colours.
But in a way you're right because the angle at D is always ...... ?
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
when I measure the one you drew on the screen I get A is 30 degrees C is 70 D is 80
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
I said #102 before seeing post #101
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
is always a right angle 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
The thing is this. There is a property that is always true for all circles and Q19 is testing it.
Amongst all your answers, you have said it correctly, but I don't want you to get it by luck, I want you to be sure.
So, looking at my multicoloured diagram, what is angle D every time?
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
Yes, that's it. Excellent!
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
You are very welcome.
By my reckoning only Q20 to go or have you done that?
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
No I did #20 and got it correct
I choose D
20. If line segment BC has a length of 24, and line segment AB has a length of 18, what is the radius of the circle? A 18 B 38 C 6 D 15 E 4 F 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
I started the next lesson about Circumference and Arc Length and I got all the 18/20 I am stuck on the 2 questions I got incorrect :
I choose C it was incorrect
What is the circumference of the circle if the radius is:
10. (x + y)pi A (x+y)/7 B (x+y)/5 C(x+y)/1 D(x+y)/2 E (x+y)/3 F (x+y)/8
So I know the the formula for the circumference of a circle is 2(pi)(r)
So it would be 2(pi)*((x + y)pi) right? but then what do I do ?
I choose A it was incorrect I am still working on the correction What is the length of the arc if 15. r=y n=x A x*y*pi/90 B x*y*pi/30 C x*y*pi/45 D x*y*pi/27 E x*y*pi/180 F x*y*pi/115
L = (n/360)(2(PI)r) where L = length, n = degree measure of arc, and r = radius of the circle.
Last edited by zeef (20121105 08:18:58)
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
Very well done for getting 18/20 at first attempt. That's really good!
I can see where you went wrong here with Q15, so I'll do it first.
I choose A it was incorrect I am still working on the correction
What is the length of the arc if
15. r=y n=x A x*y*pi/90 B x*y*pi/30 C x*y*pi/45 D x*y*pi/27 E x*y*pi/180 F x*y*pi/115
With these problems I first work out the whole circumference, and then work out the fraction for the arc.
So cancel a 2 top and bottom and it's done. Now for question 10. What is the circumference of the circle if the radius is:
10. (x + y)pi
A (x+y)/7 B (x+y)/5 C(x+y)/1 D(x+y)/2 E (x+y)/3 F (x+y)/8
So I know the the formula for the circumference of a circle is 2(pi)(r)
So it would be 2(pi)*((x + y)pi) right? but then what do I do ?
What you have done is exactly right so something else is wrong here.
If the radius has a pi in it, the circumference will collect another, giving a pi squared. None of the answers looks right.
If it's a misprint I can make sense of it. Try this:
What is the radius of the circle if the circumference is:
10. (x + y)pi
A (x+y)/7 B (x+y)/5 C(x+y)/1 D(x+y)/2 E (x+y)/3 F (x+y)/8
This way round it makes sense and one of the answers works.
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
Hi Bob,
15. r=y n=x
#15 My new answer is (E) x*y*pi/180
I pretended that x was 1 and said that (1/360 * 2= 1/180) then put the x back and multiplied. I get x*y*pi/180.
#10 OK sense I know that c=π*d and D= c/π I am going to divide the circumference by PI So I will get(x+y)π/π , and π/π = 1 so I am left with (x+y) and to get the radius I am going to divide by two and my answer is (x+y)/2.
Thank you,
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
Oh, well done. I'm so pleased. Both correct in my opinion.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
