Circle Geometry and Equations Quiz

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Questions and Answers

What is the general form of the equation for a circle given the conditions mentioned?

  • x² + y² - 2gx - 2fy + c = 0
  • x² + y² + gx + fy = 1
  • x² + y² + g + f + c = 0
  • x² + y² + 2gx + 2fy + c = 0 (correct)

Which condition must be true for a general second degree equation in two variables to represent a circle?

  • a ≠ b and h ≠ 0
  • a ≠ b and h = 0
  • a = b and h ≠ 0
  • a = b and h = 0 (correct)

If the center of a circle lies on the x-axis and has a radius of 13, what point must satisfy the equation of the circle passing through (4, 5)?

  • (0, 0)
  • (0, 13) (correct)
  • (0, 5)
  • (0, -13)

Which of the following equations represents a circle of radius 13 passing through the point (4, 5)?

<p>x² + y² - 32x - 105 = 0 (B)</p> Signup and view all the answers

What would the center coordinates be for a circle that passes through (7, 3) with a radius of 3 units and whose center lies on the line y = x - 1?

<p>(3, 2) (C)</p> Signup and view all the answers

What is the radius of a circle that touches both axes and passes through the point (1, 1)?

<p>2 (D)</p> Signup and view all the answers

If a circle touches the y-axis at (0, 2) and passes through the point (-1, 0), what is the x-coordinate of another point it passes through?

<p>(-4, 0) (C)</p> Signup and view all the answers

What is the equation of the circle inscribed in a triangle formed by the coordinate axes and the line 3x + 4y = 24?

<p>(x - 8)^2 + (y - 6)^2 = 36 (D)</p> Signup and view all the answers

Which point does not lie on the circle that touches both axes and passes through the point (1, 1)?

<p>(0, 0) (B)</p> Signup and view all the answers

What is the geometric significance of the point (0, 2) in relation to the discussed circles?

<p>A point where it touches the axis (A)</p> Signup and view all the answers

What is the equation of a circle with center at (1, 0) and radius 5?

<p>(x − 1)² + y² = 25 (A)</p> Signup and view all the answers

Which of the following represents the correct transformation of the standard circle equation x² + y² = 1 when the center is moved to (1, 2)?

<p>(x - 1)² + (y - 2)² = 1 (C)</p> Signup and view all the answers

For a circle with the diameter passing through points (0, 0) and (2, 2), what is the center of this circle?

<p>(1, 1) (C)</p> Signup and view all the answers

Which equation correctly represents the circle with center (1, 2) and a diameter of 2?

<p>(x − 1)² + (y − 2)² = 4 (D)</p> Signup and view all the answers

What is true about the normal line of a circle?

<p>It passes through the center of the circle. (C)</p> Signup and view all the answers

What is the center of the circle defined by the equation $x^2 + y^2 - 4x + 4y - 28 = 0$?

<p>(2, -2) (C)</p> Signup and view all the answers

Which of the following is the equation of a circle that is concentric with the circle $x^2 + y^2 - 6x + 12y + 15 = 0$ and has double its area?

<p>$x^2 + y^2 - 3x + 12y - 30 = 0$ (C)</p> Signup and view all the answers

What is the radius of a circle with the equation $x^2 + y^2 - 4x - 2y = eta - 5$ as defined in the problem?

<p>2 (A)</p> Signup and view all the answers

What is the general form of the equation of a circle?

<p>$x^2 + y^2 + 2gx + 2fy + c = 0$ (D)</p> Signup and view all the answers

In the equation $x^2 + y^2 + 2gx + 2fy + c = 0$, what do the variables $g$ and $f$ represent?

<p>Coordinates of the center (B)</p> Signup and view all the answers

What condition describes a circle that touches the X-axis at a point?

<p>The radius is equal to the distance from the center to the X-axis (B)</p> Signup and view all the answers

If a circle has the equation $x^2 + y^2 + 4y - 8 = 0$, what is the radius of the circle?

<p>3 (C)</p> Signup and view all the answers

What is the effect of multiplying the equation of a circle by a positive scalar?

<p>It increases the radius (C)</p> Signup and view all the answers

What is the equation of the circle whose diameter endpoints are (1, 0) and (0, 1)?

<p>x^2 + y^2 - x - y = 0 (D)</p> Signup and view all the answers

Which form of the equation represents a circle with radius r?

<p>(x - x1)^2 + (y - y1)^2 = r^2 (C)</p> Signup and view all the answers

What is the geometric significance of the diametric form of the equation of a circle?

<p>It relates the abscissae to the ordinates of the endpoints. (B)</p> Signup and view all the answers

In the parametric form of a circle, how are the coordinates of any point on the circle defined?

<p>x = r cosθ, y = r sinθ (A)</p> Signup and view all the answers

If A(cos ⍺, sin ⍺), B(cos β, sin β), and C(cos γ, sin γ) are vertices of triangle ABC, what does this represent?

<p>The orthocenter coordinates of triangle ABC. (A)</p> Signup and view all the answers

What will be the minimum radius when passing through points (1, 0) and (0, 1)?

<p>1 unit (C)</p> Signup and view all the answers

What type of line can intersect a circle according to the intercepts made by it?

<p>A secant line (A)</p> Signup and view all the answers

In the context of the general equation of a circle, what does the term (x - x1)^2 + (y - y1)^2 represent?

<p>The distance to the center from any point. (D)</p> Signup and view all the answers

Which point does the circle with its center on the line $2x - 3y + 12 = 0$ also pass through?

<p>(-3, 6) (A)</p> Signup and view all the answers

What form does a family of circles passing through the points A(x1, y1) and B(x2, y2) take?

<p>(x - x1)(x - x2) + (y - y1)(y - y2) = 0 (A)</p> Signup and view all the answers

If a circle bisects the circumference of another circle, how can the relationship between their equations be represented?

<p>S + λL = 0 (D)</p> Signup and view all the answers

To find the equation of a family of circles tangent to a given line at a point A(x1, y1), which part of the equation represents the line?

<p>L = 0 (A)</p> Signup and view all the answers

What is the general equation for a circle touching the line $x + y + 1 = 0$ at the point (1, -2)?

<p>$(x - 1)^{2} + (y + 2)^{2} + λ(x + y + 1) = 0$ (D)</p> Signup and view all the answers

In the family of circles passing through (1, 1) and (2, 2), which variable denotes an arbitrary constant?

<p>λ (A)</p> Signup and view all the answers

What is the significance of the variable 'd' in the context of a circle bisecting another circle's circumference?

<p>It is a parameter related to the second circle. (D)</p> Signup and view all the answers

Flashcards

Standard Equation of a Circle

The equation (x - h)² + (y - k)² = r² represents a circle with center (h, k) and radius r.

Central Form of a Circle Equation

Describes the relationship between a point (x, y) and the circle's center (h, k).

Circle with Center at the Origin

A circle with its center at the origin (0, 0) and radius 'r' is represented by the equation x² + y² = r².

Diameter

The diameter of a circle is a straight line passing through its center and connecting two points on the circle's boundary.

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Chord

A line that crosses a circle at two points.

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Circle touching both axes

A circle that touches both the x-axis and the y-axis.

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Radius of a circle

The distance from the center of a circle to any point on its edge.

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X-axis intercept

A point located on the x-axis where the value of y is zero.

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Origin

The point where the x-axis and y-axis intersect.

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Y-axis intercept

A point on the y-axis where the x-axis value is zero.

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General Form of the Equation of a Circle

The general form of the equation of a circle is x² + y² + 2gx + 2fy + c = 0. This can be rewritten in the standard form by completing the square.

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Circle Touching the X-axis

A circle touching the x-axis has its center on the y-axis, with the radius being the y-coordinate of the center. The equation can be derived by considering the distance from the center to the x-axis and a point on the circle.

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Circle Touching the Y-axis

A circle touching the y-axis has its center on the x-axis, with the radius being the x-coordinate of the center. The equation can be derived similarly to the previous case.

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Circle Touching X-axis at the Origin

A circle touching the x-axis at the origin has its center on the positive y-axis and its radius is equal to the y-coordinate of the center. The equation can be derived using these properties.

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Concentric Circles

If two circles are concentric, they have the same center. Modifying the constant term 'c' in the general equation will change the radius while keeping the center the same.

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What is the Standard Equation of a Circle?

The standard equation of a circle represents the relationship between the coordinates (x, y) of any point on the circle and the center (h, k) and radius (r) of the circle. It is given by: (x - h)^2 + (y - k)^2 = r^2. This equation is derived from the Pythagorean theorem applied to the distance from the center of the circle to any point on the circle.

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Define a circle.

A circle is defined as the set of all points that are equidistant from a fixed point called the center. The distance from the center to any point on the circle is called the radius.

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What is the general form of a circle's equation?

The general form of a circle's equation is x^2 + y^2 + 2gx + 2fy + c = 0. This equation is derived by expanding the standard form and rearranging terms. The parameters g, f, and c are constants. The center of the circle is determined as (-g, -f) , and the radius is calculated as r = √(g^2 + f^2 - c).

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Explain the conditions for a general second degree equation to represent a circle.

The condition for a general second degree equation in two variables to represent a circle is that the coefficients of x^2 and y^2 are equal (a = b), and the coefficient of xy is zero (h = 0). If the coefficients (a and b) are not 1, then we divide the equation by a constant to make both coefficients equal to 1. This ensures that the equation truly represents a circle.

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How do we derive the equation of a circle if we know the center?

The equation of a circle can be found if we know certain information about the circle. For example, if we know the center (h, k) and radius (r), we can directly substitute these values into the standard equation: (x - h)^2 + (y - k)^2 = r^2. Alternatively, if we know the center and a point that lies on the circle, we can substitute the coordinates of the point, along with the center's coordinates, to solve for the radius and derive the equation.

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Diametric Form of a Circle Equation

The equation of a circle with diameter endpoints A(x1, y1) and B(x2, y2) is (x - x1)(x - x2) + (y - y1)(y - y2) = 0.

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Parametric Form of a Circle Equation

A circle with radius 'r' and center (x1, y1) can be represented by the parametric equations: x = x1 + r cos θ, y = y1 + r sin θ.

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Intercepts made by a Circle

The intersection points of a circle with a line represent the intercepts made by the circle on that line.

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Family of Circles - Intersection of Circles

The equation of a circle that passes through the intersection of two given circles can be represented by combining the equations of the given circles with a weighting factor.

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Family of Circles - Two Points

The family of circles passing through two given points can be represented by adding a multiple of the equation of the line connecting the two points to the equation of a circle passing through those points.

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Family of Circles - Tangent to a Line

The equation of a circle tangent to a given line at a given point can be represented by adding a multiple of the equation of the line to the equation of a circle passing through the point.

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Intersection of Circles - Obtaining Equation

The equation of a circle passing through the intersection of two given circles can be obtained by finding the equation of the line passing through the points of intersection and then substituting it into the equation of one of the given circles.

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Intersection of Circles - Finding Points

To find the intersection of two circles, solve the system of equations formed by their equations simultaneously.

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General Equation of a Circle

The general form of a circle equation is x² + y² + 2gx + 2fy + c = 0, where (-g, -f) represents the center and √(g² + f² - c) represents the radius.

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Circle Equation - Using Intersection Points

The line x² + y² + 2gx + 2fy + c = 0 is satisfied by the points of intersection. By plugging in the known information, the equation can be solved for the unknown values.

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Study Notes

JEE 2024 Circles One Shot

  • The JEE 2024 Circles One Shot video covers various aspects of circles, including their standard equations, intercepts, notations, and the position of points relative to a circle.
  • The video also touches on families of circles and chords of circles.
  • A crash course batch for JEE Main 2024, led by experienced educators, is also advertised.
  • Standard equations of a circle are presented, including the central form: (x - x₁)² + (y - y₁)² = r². The center is (x₁, y₁) and the radius is r.
  • A circle centered at (0, 0) with radius r has the equation x² + y² = r².
  • Examples of finding circle equations given specific centers and radii, or points on the circle, are shown.
  • The diameter or normal of a circle passes through its center.
  • Practice problems involving circles, including finding the equation of a circle given certain conditions (radius, center on x or y axis, passing through a point), are shown.

Standard Equations of a Circle

  • The general equation of a circle is ax² + 2hxy + by² + 2gx + 2fy + c = 0.
  • A circle is represented by x² + y² + 2gx + 2fy + c = 0, where the center is (-g, -f) and radius is √(g² + f² − c).
  • Examples of finding the center and radius of a circle given its general equation are shown.

Intercepts Made by a Circle

  • If a circle intersects a line, AB is the length of the intercept.
  • The length of an intercept made by a circle on the x or y axis can be determined if the general equation of the circle is given as x² + y² +/- 2gx + 2fy + c = 0. This length is calculated as 2√(g² - c) where g is the term with x and c the constant.
  • A similar formula exists for intercept length on the y axis.
  • A circle's center will lie on a line cutting the circle's intercept, if the line is the chord of the circle

Family of Circles

  • A family of circles includes circles that share common properties. The family can be defined in various ways, for example, it can pass through the intersections of two circles or through the intersection of a line and a circle.

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