Math Problem Statement

In the following figure, the circle is centered at A with a radius of 60 units. Points A, C, D, and P are all on the same line. B and D are on the circle. ∠CBD ≅ ∠DBP. What is the product AC × AP?

Solution

To solve this problem, we can use properties of circles and similar triangles. Here’s the step-by-step approach:

  1. Understand the configuration:

    • The circle is centered at AA with radius 60 units.
    • Points AA, CC, DD, and PP lie on a straight line, and points BB and DD lie on the circle.
    • CBDDBP\angle CBD \cong \angle DBP.
  2. Identify key angle properties:

    • Since CBDDBP\angle CBD \cong \angle DBP, triangle CBDCBD and triangle DBPDBP are similar by the Angle-Angle (AA) similarity criterion.
    • This similarity implies that ACAP=CDDP\frac{AC}{AP} = \frac{CD}{DP} (since similar triangles have proportional sides).
  3. Apply the Power of a Point theorem:

    • The Power of a Point theorem states that if a point (here, CC) lies outside a circle, and two line segments (here, CDCD and CPCP) are drawn such that they intersect the circle, then AC×AP=(radius)2AC \times AP = (radius)^2.
    • Since AA is the center and the radius is 60 units, we have: AC×AP=602=3600.AC \times AP = 60^2 = 3600.

Thus, the product AC×AP=3600AC \times AP = 3600.

Would you like a more detailed breakdown or have any questions?


Here are some related questions to deepen understanding:

  1. What is the Power of a Point theorem and how is it applied?
  2. How does the Angle-Angle similarity criterion work in triangle similarity?
  3. Can you prove why similar triangles have proportional corresponding sides?
  4. Why does knowing the radius allow us to find AC×APAC \times AP directly?
  5. What other geometric configurations can the Power of a Point theorem be applied to?

Tip: Remember that the Power of a Point theorem is a powerful tool in circle geometry, helping to relate distances of points inside or outside a circle to the radius.

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Math Problem Analysis

Mathematical Concepts

Circle Geometry
Similar Triangles
Power of a Point

Formulas

Power of a Point: AC × AP = radius²

Theorems

Angle-Angle Similarity
Power of a Point Theorem

Suitable Grade Level

Grades 9-12