Calculate Circle Diameter Given Two Chords: AX=BX=6 cm, CX=4 cm, DX=9 cm

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    Circle Diameter
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Homework Help Overview

The problem involves two chords of a circle, AB and CD, intersecting at point X, with given lengths for segments AX, BX, CX, and DX. Participants are tasked with calculating the radius of the circle, which is stated to have an integer value.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the application of the intersecting secant theorem and the construction of tangents and diameters. Some express confusion about the original poster's approach and the relevance of the tangent and diameter drawn. Others question the assumption about the perpendicularity of the chords and the sufficiency of the information provided.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem setup. Some suggest that there may not be enough information to definitively determine the radius, while others propose potential reasoning based on the relationships between the segments. A few participants express uncertainty about the assumptions made regarding the chords and their configurations.

Contextual Notes

There is a mention of a specific section in a book related to intersecting chords and secant theorems, which may impose certain constraints or expectations on the problem-solving approach. Additionally, the original poster notes the need for further information regarding the lengths of certain segments to progress.

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Two chords of a circle, AB and CD, intersect at X, such that AX=BX= 6 cm. CX=4 cm and DX=9 cm. Calculate the radius of the circle, given that it has an integer value. I constructed a secant EG of a diameter FG of the circle and drew a tangent from C to it at E, then we have from the intersecting secant theroem: EFxEG=EC^2.Many thanks guys.
 
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I don't understand your work.
 
All I did was to draw a tangent at point C, to the circle, then drew a diameter FG of the circle such that, when you produce the diameter GF it meets the tangent at E.Sorry for the long delay in reply. Many thanks.
 
Is FG just any diamater that isn't parallel to the tangent at C? And I don't see why you did what you did.
 
The reason why I have done what I did, was that this question is posed in the section of a book called "intersecting chord and secant theorems".Even though I would need to know the length EF and the tangent |EC|. Since I don't the solution to the problem eludes me.Maybe someone could start me off!
 
The radius is quite guessable from observing that the lengths of the 4 segments satisfy Archimedis' lemma for perpendicular chords.
 
The chords aren't necessarily perpendicular (are they?).
 
No, the chords aren't necessarily perpendicular. The answer is 10cm. The question is how did they get it!
 
I don't think there's enough information here. Take any circle of sufficiently large size (this will be clear in a minute). Draw a chord of length 12, and call the endpoints A and B. Then draw a line from the center of this chord X, to a point C on on the arc between A and B, such that the length of CX is 4. Note this is possible since the maximum length such a segment could have is clearly 6, and the minimum can be made arbitrarily small by increasing the radius of the circle. Now extend this line to intersect the circle again at a point D, and since AX*BX=CX*DX, we must have DX=9. Am I misssing something, or is this exactly the setup you've described? Maybe you're asked to find the smallest such circle?
 
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StatusX said:
I don't think there's enough information here. Take any circle of sufficiently large size (this will be clear in a minute). Draw a chord of length 12, and call the endpoints A and B. Then draw a line from the center of this chord X, to a point C on on the arc between A and B, such that the length of CX is 4. Note this is possible since the maximum length such a segment could have is clearly 6, and the minimum can be made arbitrarily small by increasing the radius of the circle. Now extend this line to intersect the circle again at a point D, and since AX*BX=CX*DX, we must have DX=9. Am I misssing something, or is this exactly the setup you've described? Maybe you're asked to find the smallest such circle?

But then the smallest such circle would be one in which the longest chord is diameter, andthe radius would be equal to 6.5.

I agree, there is not enough information.
 

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