Math Problem Statement

Find equations for the circle and the line in the given figure, where the circle is centered at the origin and passes through the point (-5, 12), and the line is perpendicular to the radius at that point.

Solution

In the given figure, we need to find the equations for both the circle and the line.

1. Equation of the Circle:

The circle is centered at the origin, (0,0)(0, 0), and passes through the point (5,12)(-5, 12).

The general equation of a circle with center (h,k)(h, k) and radius rr is: (xh)2+(yk)2=r2(x - h)^2 + (y - k)^2 = r^2 Since the center is at (0,0)(0, 0), the equation simplifies to: x2+y2=r2x^2 + y^2 = r^2

We can determine rr by finding the distance from the center (0,0)(0, 0) to the point (5,12)(-5, 12), which lies on the circle: r=(50)2+(120)2=25+144=169=13r = \sqrt{(-5 - 0)^2 + (12 - 0)^2} = \sqrt{25 + 144} = \sqrt{169} = 13

Thus, the equation of the circle is: x2+y2=132=169x^2 + y^2 = 13^2 = 169 x2+y2=169x^2 + y^2 = 169

2. Equation of the Line:

The line is passing through the point (5,12)(-5, 12) and is perpendicular to the radius of the circle at that point. The slope of the radius from the center (0,0)(0, 0) to (5,12)(-5, 12) is: slope of radius=12050=125\text{slope of radius} = \frac{12 - 0}{-5 - 0} = -\frac{12}{5}

Since the line is perpendicular to the radius, its slope will be the negative reciprocal of 125-\frac{12}{5}, which is: slope of line=512\text{slope of line} = \frac{5}{12}

Now, using the point-slope form of a line equation: yy1=m(xx1)y - y_1 = m(x - x_1) Substituting (5,12)(-5, 12) and the slope 512\frac{5}{12}: y12=512(x+5)y - 12 = \frac{5}{12}(x + 5)

Expanding this equation: y12=512x+2512y - 12 = \frac{5}{12}x + \frac{25}{12} Multiplying the entire equation by 12 to eliminate the fraction: 12y144=5x+2512y - 144 = 5x + 25 Rearranging: 5x12y=1695x - 12y = -169

Thus, the equation of the line is: 5x12y=1695x - 12y = -169

Summary:

  • The equation of the circle is: x2+y2=169x^2 + y^2 = 169
  • The equation of the line is: 5x12y=1695x - 12y = -169

Would you like more details or have any other questions?

Here are some related questions:

  1. How do you determine the radius of a circle given its center and a point on the circle?
  2. What is the significance of the negative reciprocal in the slope of perpendicular lines?
  3. How do you derive the general equation of a line from the point-slope form?
  4. What other geometric properties can be derived from a circle and a tangent line?
  5. How can you verify if a point lies on both the circle and the line?

Tip: Always check if a line is tangent to a circle by verifying that the distance between the center of the circle and the line equals the radius of the circle.

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Equations of Circles
Slopes and Perpendicularity

Formulas

Equation of a circle: (x - h)^2 + (y - k)^2 = r^2
Slope of a line: (y2 - y1) / (x2 - x1)
Point-slope form of a line: y - y1 = m(x - x1)

Theorems

Pythagorean Theorem (to calculate radius)
Perpendicular slopes have negative reciprocal

Suitable Grade Level

Grades 9-11