altitude (of a plane figure)

NOVEMBER 14, 2023

Altitude (of a Plane Figure) in Math: Definition

Definition

In mathematics, the altitude of a plane figure refers to the perpendicular distance from a vertex of the figure to the opposite side or base. It is commonly used in geometry to determine various properties and measurements of triangles, quadrilaterals, and other polygons.

History

The concept of altitude has been studied and used in mathematics for centuries. Ancient Greek mathematicians, such as Euclid and Pythagoras, made significant contributions to the understanding and application of altitude in geometry. Over time, the concept has evolved and been refined, leading to its current usage in modern mathematics.

Grade Level

The concept of altitude is typically introduced in middle school or early high school mathematics, around grades 7-9. It is an important topic in geometry and is often covered in introductory geometry courses.

Knowledge Points and Explanation

The concept of altitude involves several key knowledge points:

  1. Perpendicularity: The altitude is always perpendicular to the base or side of the figure it is drawn from.
  2. Triangle Altitude: In a triangle, each side can have its own altitude, and they are concurrent at a single point called the orthocenter.
  3. Quadrilateral Altitude: In a quadrilateral, the altitude can be drawn from any vertex to the opposite side, creating four altitudes.
  4. Polygon Altitude: The altitude can also be extended to other polygons, such as pentagons, hexagons, etc., by drawing perpendicular lines from vertices to their opposite sides.

Types of Altitude

Altitudes can be classified based on the type of figure they are drawn in:

  1. Triangle Altitude: Each side of a triangle can have its own altitude, resulting in three altitudes.
  2. Quadrilateral Altitude: In a quadrilateral, each vertex can have an altitude drawn to the opposite side, resulting in four altitudes.
  3. Polygon Altitude: For polygons with more than four sides, each vertex can have an altitude drawn to the opposite side, resulting in multiple altitudes.

Properties of Altitude

Some important properties of altitude include:

  1. The altitude is always perpendicular to the base or side it is drawn from.
  2. In a triangle, the three altitudes are concurrent at a point called the orthocenter.
  3. The length of an altitude can be used to calculate the area of a triangle or other polygons.

Finding or Calculating Altitude

To find or calculate the altitude of a plane figure, follow these steps:

  1. Identify the vertex from which the altitude is to be drawn.
  2. Determine the base or side to which the altitude is perpendicular.
  3. Measure the perpendicular distance from the vertex to the base or side.

Formula or Equation for Altitude

The formula for calculating the altitude of a triangle is:

Altitude = (2 * Area) / Base

Where "Area" represents the area of the triangle and "Base" represents the length of the base.

Symbol or Abbreviation

There is no specific symbol or abbreviation exclusively used for altitude. However, it is often represented by the letter "h" in mathematical equations or diagrams.

Methods for Altitude

There are several methods for finding or drawing altitudes, depending on the given figure and the information provided. Some common methods include:

  1. Using the Pythagorean theorem to calculate the length of the altitude in a right triangle.
  2. Applying trigonometric ratios, such as sine, cosine, or tangent, to find the length of the altitude in non-right triangles.
  3. Utilizing the properties of similar triangles to determine the length of the altitude in various polygons.

Solved Examples on Altitude

  1. Example 1: Find the altitude of an equilateral triangle with a side length of 6 cm. Solution: Since the triangle is equilateral, all sides are equal. Using the formula, Altitude = (2 * Area) / Base, we can calculate the area of the triangle as (sqrt(3) / 4) * (6^2) = 9sqrt(3) cm^2. The base length is 6 cm. Substituting these values into the formula, we get Altitude = (2 * 9sqrt(3)) / 6 = 3sqrt(3) cm.

  2. Example 2: In a right-angled triangle with a base of 8 cm and height of 6 cm, find the length of the altitude drawn to the hypotenuse. Solution: The altitude drawn to the hypotenuse divides the triangle into two smaller triangles. Using the Pythagorean theorem, we can find the length of the altitude as sqrt(8^2 - 6^2) = sqrt(64 - 36) = sqrt(28) = 2sqrt(7) cm.

  3. Example 3: Find the altitude of a trapezoid with bases measuring 10 cm and 6 cm, and a height of 4 cm. Solution: The altitude of a trapezoid is the perpendicular distance between the bases. In this case, the altitude is equal to the given height of 4 cm.

Practice Problems on Altitude

  1. Find the altitude of an isosceles triangle with a base of 12 cm and equal sides measuring 10 cm.
  2. In a quadrilateral with sides measuring 5 cm, 6 cm, 7 cm, and 8 cm, find the length of the altitude drawn from the vertex opposite the side measuring 7 cm.
  3. Calculate the altitude of a regular hexagon with a side length of 9 cm.

FAQ on Altitude

Q: What is the altitude of a plane figure? A: The altitude of a plane figure refers to the perpendicular distance from a vertex of the figure to the opposite side or base.

Q: How is altitude used in mathematics? A: Altitude is used to determine various properties and measurements of triangles, quadrilaterals, and other polygons, such as area calculations and determining the orthocenter of a triangle.

Q: Can the altitude be drawn from any vertex of a polygon? A: Yes, the altitude can be drawn from any vertex of a polygon to its opposite side, creating multiple altitudes.

Q: Is there a specific formula for calculating the altitude of a quadrilateral? A: No, there is no specific formula for calculating the altitude of a quadrilateral. The altitude is simply the perpendicular distance between a vertex and the opposite side.

Q: Can the altitude of a triangle be outside the triangle? A: No, the altitude of a triangle is always drawn within the triangle, from a vertex to the opposite side.

Q: Are all altitudes of a triangle equal in length? A: No, the altitudes of a triangle can have different lengths, depending on the lengths of the sides and the angles of the triangle.