Math Problem Statement

Work out the length of DC given AB = 16 cm, BP = 14 cm, and CP = 12 cm, where ABP and DCP are straight lines, and A, B, C, and D are points on a circle.

Solution

To solve for DCDC in this problem, we can use the intersecting chords theorem. The theorem states that if two chords intersect inside a circle, the products of the lengths of the segments of each chord are equal.

In this problem:

  • The two intersecting chords are ABAB and CDCD.
  • Given: AB=16cm,BP=14cm,CP=12cmAB = 16 \, \text{cm}, \quad BP = 14 \, \text{cm}, \quad CP = 12 \, \text{cm}

Let’s denote:

  • AP=AB+BP=16+14=30cmAP = AB + BP = 16 + 14 = 30 \, \text{cm}
  • Let DP=DC+CPDP = DC + CP, where DCDC is what we want to find.

According to the intersecting chords theorem: AB×BP=CP×DCAB \times BP = CP \times DC Substituting the given values: 16×14=12×DC16 \times 14 = 12 \times DC 224=12×DC224 = 12 \times DC DC=22412=18.67cmDC = \frac{224}{12} = 18.67 \, \text{cm}

Therefore, the length of DCDC is approximately 18.67cm18.67 \, \text{cm}.

Would you like further clarification, or do you have any questions?

Here are some related questions:

  1. How does the intersecting chords theorem apply to other shapes?
  2. What are some alternative methods to find unknown lengths in circle geometry?
  3. How can the intersecting chords theorem be proven?
  4. Are there situations where the intersecting chords theorem does not apply?
  5. Can this theorem be extended to non-circular shapes?

Tip: The intersecting chords theorem is useful for any configuration where two chords intersect, whether or not they form straight lines outside the circle.

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Math Problem Analysis

Mathematical Concepts

Geometry
Circle Theorems
Intersecting Chords Theorem

Formulas

AB × BP = CP × DC

Theorems

Intersecting Chords Theorem

Suitable Grade Level

Grades 9-11