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Co-ordinate Geometry Formula

1. Distance Formula: Distance(d) between two points A(x1, y1) and B(x2, y2) is given by
AB =
(x2 - x1)2 + (y2 - y1)2
2.Section Formula: Coordinate of a point P(x, y) which divides the line joining two points (x1, y1) and (x2, y2) in the ratio of m:n internally and externally are given by
Internally: P(x, y) = 
mx1 + nx2
m + n
my1 + ny2
m + n
Externally: P(x, y) = 
mx1 - nx2
m - n
my1 - ny2
m - n
3.Mid-Point Formula: Mid-point P(x, y) of the line joining two points (x1, y1) and (x2, y2) is given by
P(x, y) = 
x1 + x2
2
y1 + y2
2
4.Centroid of a Triangle: Centroid P(x, y) of a triangle with vertices (x1, y1), (x2, y2) and (x3, y3) is given by
P(x, y) = 
x1 + x2 + x3
3
y1 + y2 + y3
3
5.Slope of a Line Formula:
a. Slope of a straight line which makes angle θ with x-axis in positive direction is given by
Slope(m) = tanθ
b. Slope of a straight line passing through the points (x1, y1) and (x2, y2) is given by
Slope(m) = 
y2 - y1
x2 - x1
c. Slope of a straight line ax + by + c = 0 is given by
Slope(m) = 
a
b
6.Slope Intercept Form: Equation of a straight line with slope m and y-intercept c is given by
y = mx + c
7.Double Intercept Form: Equation of a traight line with x-intercept a and y-intercept b is given by
x
a
 + 
y
b
 = 1
8.Normal Form: Equation of a straight line with perpendicular from origin p and angle of perpendicular with x-axis α is given by
xcosα + ysinα = p
9.Point Slope Form: Equation of a straight line with m and passing through the point (x1, y1) is given by
y – y1 = m(x – x1)
10.Two Points Form: Equation of a straight line passing through the points (x1, y1) and (x2, y2) is given by
y – y1
y2 - y1
x2 - x1
 (x – x1)
11.Perpenducular Distance:
a. Perpendicular distance(d) from the point (x1, y1) to the line xcosα + ysinα = p is given by
d = ±(x1cosα + y1sinα – p)
b. Perpendicular distance(d) from the point (x1, y1) to the line Ax + By + C = 0 is given by
d = ± 
Ax1 + By1 + C
A2 + B2
12.Area of Triangle: Area of triangle with vertices (x1, y1), (x2, y2) and (x3, y3) is given by
Δ = 
1
2
[(x1y2 - x2y1) + (x2y3 - x3y2) + (x3y1 - x1y3)]
13.Area of Quadrilateral: Area of quadrilateral with vertices (x1, y1), (x2, y2), (x3, y3) and (x4, y4) is given by
1
2
[(x1y2 - x2y1) + (x2y3 - x3y2) + (x3y4 - x4y3) + (x4y1 - x1y4)]
14.Angle Between Two Straight Lines: Angle between two straight lines with slope m1 and m2 is given by
θ = tan-1
± 
m1 - m2
1 + m1m2
Cor1: when m1 = m2, the lines are parallel or coincident.
Cor2: when m1×m2 = -1, the lines are perpendicular.
15.Equation of a Circle:
a. Equation of a circle with center at origin O(0, 0) and radius r is given by
x2 + y2 = r2
b. Equation of a circle with center at any point (h, k) and radius r is given by
x2 + y2 +2gx + 2fy + c = 0
Where where, g = -h, f = -k, and c = h2 + k2 + r2
16.Equation of a Circle in Diameter Form: Equation of a circle with two end points of a diameter (x1, y1) and (x2, y2) is given by
(x – x1)(x – x2) + (y – y1)(y – y2) = 0

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Navigating the Plane: Your Comprehensive Guide to Coordinate Geometry Formulas

Coordinate geometry, also known as analytic geometry, bridges the gap between algebra and geometry by using a coordinate system to represent points and geometric figures on a plane. Mastering the formulas of coordinate geometry is fundamental for understanding and solving a wide range of mathematical problems. This comprehensive guide provides a clear and concise overview of essential coordinate geometry formulas, empowering you to navigate the plane with confidence.

Understanding the Coordinate Plane: Axes and Points

Before diving into the formulas, let's recap the basics of the coordinate plane:

  • Axes: The coordinate plane is defined by two perpendicular lines, the x-axis (horizontal) and the y-axis (vertical).
  • Origin: The point where the x-axis and y-axis intersect (0,0).
  • Coordinates: Points on the plane are represented by ordered pairs (x, y), where 'x' is the distance along the x-axis and 'y' is the distance along the y-axis.

Essential Coordinate Geometry Formulas:

Here's a breakdown of the key formulas you'll need:

  • Distance Formula: Calculates the distance between two points (x₁, y₁) and (x₂, y₂).

    • Distance = √((x₂ - x₁)² + (y₂ - y₁)²)
  • Midpoint Formula: Calculates the coordinates of the midpoint of a line segment joining two points (x₁, y₁) and (x₂, y₂).

    • Midpoint = ((x₁ + x₂)/2, (y₁ + y₂)/2)
  • Slope Formula: Calculates the slope (m) of a line passing through two points (x₁, y₁) and (x₂, y₂). The slope represents the steepness of the line.

    • Slope (m) = (y₂ - y₁) / (x₂ - x₁)

Equations of a Line:

There are several forms for the equation of a straight line:

  • Slope-Intercept Form: y = mx + b, where 'm' is the slope and 'b' is the y-intercept (the point where the line crosses the y-axis).
  • Point-Slope Form: y - y₁ = m(x - x₁), where 'm' is the slope and (x₁, y₁) is a point on the line.
  • Two-Point Form: (y - y₁) / (x - x₁) = (y₂ - y₁) / (x₂ - x₁), where (x₁, y₁) and (x₂, y₂) are two points on the line.
  • General Form: Ax + By + C = 0, where A, B, and C are constants.

Illustrative Examples: Putting Formulas into Practice

Let's work through some examples to understand how to apply these formulas:

  • Example 1: Find the distance between the points (2, 3) and (5, 7).

    • Distance = √((5 - 2)² + (7 - 3)²) = √(3² + 4²) = √25 = 5
  • Example 2: Find the midpoint of the line segment joining the points (1, 4) and (7, 2).

    • Midpoint = ((1 + 7)/2, (4 + 2)/2) = (4, 3)
  • Example 3: Find the slope of the line passing through the points (2, 5) and (6, 13).

    • Slope (m) = (13 - 5) / (6 - 2) = 8 / 4 = 2
  • Example 4: Find the equation of the line with a slope of 3 and passing through the point (4, -1) using the point-slope form.

    • y - (-1) = 3(x - 4) => y + 1 = 3x - 12 => y = 3x - 13
  • Example 5: Find the equation of the line passing through the points (2, 3) and (5, 7) using the two-point form.

    • (y - 3) / (x - 2) = (7 - 3) / (5 - 2) => (y - 3) / (x - 2) = 4/3 => 3(y-3) = 4(x-2) => 3y - 9 = 4x - 8 => 4x - 3y + 1 = 0

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Applications of Coordinate Geometry:

Coordinate geometry has applications in various fields, including:

  • Navigation: Used in GPS systems and mapmaking.
  • Computer Graphics: Creating and manipulating images on screens.
  • Physics: Describing the motion of objects.
  • Engineering: Designing structures and systems.

Conclusion: Mastering Coordinate Geometry

Understanding coordinate geometry is essential for solving a wide range of mathematical problems and has practical applications in many fields. This guide provides a valuable resource for learning and applying these fundamental formulas. By mastering these concepts, you'll be better equipped to tackle challenges in mathematics, science, engineering, and various real-world applications.

Call to Action:

Bookmark this page for quick reference and share it with others who might find it helpful. Practice applying these formulas to different coordinate geometry problems to reinforce your understanding. Visualizing points and lines on the coordinate plane will solidify your grasp of these concepts.