Math Problem Statement

A circle is centered at $O.$ The tangent to the circle at $P$ is extended to $Q.$ Line segment $\overline{QS}$ intersects the circle at $R.$ Find the area of the circle.

[asy] unitsize(2.5 cm);

pair A, B, C, D, E, F, G, O;

A = dir(70); B = A + 1.2dir(-20); C = dir(25); D = 2C - B; O = (0,0);

draw(Circle(O,1)); draw(A--B--D--O);

dot("$P$", A, N); dot("$Q$", B, dir(0)); dot("$R$", C, SW); dot("$S$", D, NW); dot("$O$", O, SW); label("$3$", (D + O)/2, NW, red); label("$4$", (C + D)/2, S, red); label("$4$", (B + C)/2, S, red); label("$8$", (A + B)/2, N, red); [/asy]

Solution

We are given a circle centered at OO, with a tangent at point PP. The tangent is extended to point QQ, and line segment QS\overline{QS} intersects the circle at point RR. We are tasked with finding the area of the circle.

Step 1: Analyze the diagram

The diagram provides the following key information:

  • OPOP is the radius of the circle, as PP lies on the circle and OPOP is perpendicular to the tangent at PP.
  • PQ=8PQ = 8, which is the length of the tangent from PP to QQ.
  • The segment QSQS is extended and intersects the circle at RR.
  • The segment OR=3+4=7OR = 3 + 4 = 7, where the distances OROR are the sum of the two smaller segments 33 and 44.

Step 2: Apply the Power of a Point Theorem

The Power of a Point Theorem states that the power of point QQ with respect to the circle is equal to the product of the lengths of the segments of the line QR\overline{QR} that intersects the circle. Specifically, the theorem gives:

QPQS=OP2QP \cdot QS = OP^2

From the problem:

  • PQ=8PQ = 8
  • QS=3+4=7QS = 3 + 4 = 7
  • The radius OP=rOP = r, which is what we need to find.

Step 3: Set up the equation

Using the Power of a Point Theorem, we substitute the known values:

87=r28 \cdot 7 = r^2

This simplifies to:

56=r256 = r^2

Step 4: Solve for rr

To find the radius rr, take the square root of both sides:

r=56=214r = \sqrt{56} = 2\sqrt{14}

Step 5: Calculate the area of the circle

The area AA of a circle is given by the formula:

A=πr2A = \pi r^2

Substitute r2=56r^2 = 56:

A=π×56=56πA = \pi \times 56 = 56\pi

Thus, the area of the circle is 56π\boxed{56\pi}.


If you'd like further details or have any questions, feel free to ask! Here are some related questions:

  1. How does the Power of a Point Theorem work for tangents to a circle?
  2. What is the geometric significance of the length of a tangent from a point outside the circle?
  3. Can we apply the Power of a Point Theorem in other geometric configurations? Provide examples.
  4. How do we calculate the area of a circle if we know the length of a chord and its perpendicular distance from the center?
  5. What other properties of tangents to circles can help solve geometric problems?

Tip: In geometry, understanding the properties of tangents and secants to a circle can significantly simplify the solution process for many problems involving circles!

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Math Problem Analysis

Mathematical Concepts

Geometry
Circles
Tangents
Power of a Point Theorem

Formulas

Power of a Point: QP * QS = OP^2
Area of a Circle: A = \pi r^2

Theorems

Power of a Point Theorem
Properties of Tangents to a Circle

Suitable Grade Level

Grades 9-11