Math Problem Statement

Show that the points (1,2), (3,-4), (5,-8), and (19,8) are concyclic.

Solution

The image contains a problem focused on demonstrating that a set of given points are concyclic, meaning they all lie on a common circle.

Here's a breakdown of the approach:

  1. General Circle Equation: The equation of a circle is generally given by: x2+y2+2gx+2fy+c=0x^2 + y^2 + 2gx + 2fy + c = 0 Where gg, ff, and cc are constants to be determined.

  2. Given Points: The points provided are A(1,2)A(1, 2), B(3,4)B(3, -4), C(5,8)C(5, -8), and D(19,8)D(19, 8).

  3. Substitution into the Circle Equation: To prove the points lie on the same circle, we substitute each point into the circle equation. By substituting the coordinates, a system of linear equations in terms of gg, ff, and cc is formed.

  4. First Substitution (Point A(1,2)A(1, 2)): Substitute (1,2)(1, 2) into the general equation: 12+22+2g(1)+2f(2)+c=01^2 + 2^2 + 2g(1) + 2f(2) + c = 0 Simplifying this gives: 1+4+2g+4f+c=01 + 4 + 2g + 4f + c = 0 2g+4f+c+5=0(Equation 1)2g + 4f + c + 5 = 0 \quad \text{(Equation 1)}

  5. Second Substitution (Point B(3,4)B(3, -4)): Substitute (3,4)(3, -4) into the general equation: 32+(4)2+2g(3)+2f(4)+c=03^2 + (-4)^2 + 2g(3) + 2f(-4) + c = 0 Simplifying this gives: 9+16+6g8f+c=09 + 16 + 6g - 8f + c = 0 6g8f+c+25=0(Equation 2)6g - 8f + c + 25 = 0 \quad \text{(Equation 2)}

  6. Third Substitution (Point C(5,8)C(5, -8)): Substitute (5,8)(5, -8) into the general equation: 52+(8)2+2g(5)+2f(8)+c=05^2 + (-8)^2 + 2g(5) + 2f(-8) + c = 0 Simplifying this gives: 25+64+10g16f+c=025 + 64 + 10g - 16f + c = 0 10g16f+c+89=0(Equation 3)10g - 16f + c + 89 = 0 \quad \text{(Equation 3)}

Next Steps:

You would typically solve this system of linear equations (Equations 1, 2, and 3) for gg, ff, and cc. After solving these, if the constants satisfy the equation when the fourth point D(19,8)D(19, 8) is substituted, all points are concyclic.

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Math Problem Analysis

Mathematical Concepts

Analytic Geometry
Circle Equations
Linear Algebra

Formulas

Equation of a circle: x^2 + y^2 + 2gx + 2fy + c = 0
Substitution of coordinates to form linear equations

Theorems

Points are concyclic if they lie on the same circle, which can be proven by satisfying the general equation of a circle.

Suitable Grade Level

Grade 10-12