Math Problem Statement

The diagram shows a circle with center A passing through point B. A second circle has center B and passes through A. The tangent at B to the first circle intersects the second circle at C and D. The coordinates of A are (-1, 4) and the coordinates of B are (3, 2). (a) Find the equation of the tangent CBD.

Solution

The problem you’ve provided discusses two circles and asks to find the equation of the tangent CBDCBD. Let's break it down based on the information given:

Information:

  1. First circle: Center A(1,4)A(-1, 4), passes through point B(3,2)B(3, 2).
  2. Second circle: Center B(3,2)B(3, 2), passes through point A(1,4)A(-1, 4).
  3. The tangent at BB to the first circle intersects the second circle at points CC and DD.

(a) To find the equation of the tangent CBDCBD:

We know that the tangent at point BB is perpendicular to the radius at BB, so we need to:

  1. Find the slope of the radius from AA to BB. This is the slope of the line passing through A(1,4)A(-1, 4) and B(3,2)B(3, 2): mAB=243(1)=24=12m_{\text{AB}} = \frac{2 - 4}{3 - (-1)} = \frac{-2}{4} = -\frac{1}{2}
  2. The slope of the tangent will be the negative reciprocal of the slope of ABAB, because the tangent is perpendicular to the radius: mtangent=2m_{\text{tangent}} = 2
  3. Now, using the point-slope form of a line equation yy1=m(xx1)y - y_1 = m(x - x_1), where the point is B(3,2)B(3, 2) and the slope is 2: y2=2(x3)y - 2 = 2(x - 3) Simplifying: y2=2x6y - 2 = 2x - 6 y=2x4y = 2x - 4 Thus, the equation of the tangent CBDCBD is: y=2x4y = 2x - 4

Would you like a detailed breakdown of the next part or have any questions on this?

Follow-up Questions:

  1. How do we find the radius of a circle given two points?
  2. What is the general equation of a circle?
  3. How do we determine if a line is tangent to a circle geometrically?
  4. What is the significance of the point of tangency in this context?
  5. How can we calculate the coordinates of CC and DD?

Tip:

Remember, the slope of a tangent to a circle is always the negative reciprocal of the slope of the radius at the point of tangency!

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Math Problem Analysis

Mathematical Concepts

Geometry
Circles
Tangents
Slope of a Line

Formulas

Slope formula: m = (y2 - y1) / (x2 - x1)
Point-slope form: y - y1 = m(x - x1)
Equation of a tangent line

Theorems

The tangent to a circle is perpendicular to the radius at the point of tangency

Suitable Grade Level

Grades 10-12