Right angle

Right angle
Table of Contents

Introduction 

right angle

A right angle has an angle that measures exactly 90 degrees.

right angle

Right angles are observed in polygons such as triangles, squares, rectangles and other quadrilaterals. The symbol ‘?’ denotes the 90o angle.

Right angles are among the most commonly observable angles around us. It can be seen in door frames, book corners or a cardboard among others.

Properties of Right Angles

right angle
  • A right-angle measure exactly 90o or ?/2 radians.
right angle
  • The two arms of a right angle are perpendicular to each other. They intersect at a 90o angle.
  • The right-angle measure is exactly half of a straight angle, which measures 180 degrees.
right angle
  • The sum of the value of complementary angles is 90o.
right angle
  • Two right angles are supplementary to each other. This is because the sum of the two angles is 180o.
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  • In a right-angle triangle –
    • The side opposite to the right angle is called a hypotenuse.
    • The angle formed between the perpendicular (opposite side) and base (adjacent side) is the right angle.
    • The hypotenuse is the longest side.
    • The interior angles opposite to the right angle in the triangle are complementary and their value will be 90o.
    • The two angles opposite the right angles are always acute angles.
right angle
  • In quadrilateral polygons with equal angles all four angles will be right angles. For example, square and rectangle.

Examples of Right Angles

right angle
  • Most conventional doors are rectangular shaped and have right angles in the corners.
  • Football, baseball, badminton courts and tennis courts have rectangular shapes and right angles.
  • Where the tree is rooted in the ground, a right angle can be observed.
  • The straight-backed chair legs are generally perpendicular to the seat and form a right angle.
  • Every step in a staircase has a right angle.
  • Street intersections and crossroads form 90o angles.

Tools used for measuring right angles in everyday life

right angle
  • Protractor - A protractor is used to measure angles. The protractor is a semi-circle which forms a 180o straight angle at the base. The highest point of its circumference divides the protractor into exactly two halves, forming a right angle at the centre.
right angle
  • Inclinometer – it is used to measure slopes, tilts and angles by engineers, architects, masons, and electricians.
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  • Speed square – it is used largely by carpenters for marking cutlines.
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  • Pivot square – they have pivoting arms that swing to align with the required angle between 0o and 90o. It is used for levelling in carpentry and masonry, roof tiling, plumbing cuts etc.
right angle
  • Square shooter – this is a precision angle tool used for shooting or aligning perfect square angles. It has a base that aligns with one edge and an adjustable arm that swings out.

The Pythagorean Theorem and Right Angles

The Pythagorean theorem states in a right-angled triangle the square of the hypotenuse is equal to the sum of the squares of the other two sides.

right angle

In the above right-angle triangle ?ABC –

c2 = a2 + b2??

Here, ????

b is the base,

a is the perpendicular (height)

c is the hypotenuse

Example: Two beams are placed perpendicular to one another such that they form a right angle at their point of intersection. If beam 1 is 6 feet and beam 2 is 8 feet, what will be the measure of the support beam?

A diagram of beam support
Description automatically generated

In the above problem, beam 1 is the altitude and beam 2 is the base of a right-angle triangle. So, the support beam which is opposite to the right angle will form the hypotenuse.

As per Pythagoras theorem,

right angle

h2 = p2 + b2

thus,

support beam = (6)2 + (8)2

                         = 36 + 64

                         = 100

Thus, the measure of the support beam is 100 feet.

Pythagoras theorem is extensively used by architects and civil engineers in the construction of buildings, bridges, roofs etc. In two-dimensional navigation, the Pythagorean theorem helps in finding the shortest distance between two lengths. For instance, on a sea route, if the captain is navigating to a point that is 350 km north and 430 km to the west. To understand the distance from the ship to the point and calculate how many degrees to the west from the north the ship would need to follow to reach that point.

N

If the point of intersection of the north leg and the west leg is considered to be x and it forms a right angle, then the shortest line connecting them will be the hypotenuse. This principle can be used for air navigation. For instance, a plane can use its height above the ground and its distance from the landing lane at the airport to find the correct place to begin a descent to that airport.

Right Angles in Coordinate Geometry - Cartesian Plane

In coordinate geometry, you can identify and work with right angles on the Cartesian plane. This is done by understanding relationships between lines and applying geometric properties. Right angles are crucial in coordinate geometry, particularly when defining axes (x-axis and y-axis) and plotting points. 

right angle

The Cartesian Coordinate System is also known as the rectangular coordinate system because of the right angles formed by the axes and grid lines. The two-dimensional plane where the x-axis and y-axis meet at a right angle is called the origin. Further, each horizontal line in the grid intersects each vertical line in the grid at a right angle. The Cartesian Coordinate System is fundamental in fields like computer graphics, navigation, and design, where precise measurements and perpendicularity are required.

right angle

The 2-D cartesian coordinates are often used on maps to identify the equator, latitude and longitude. The individual grids are also used for plotting areas and identifying landmarks among others.

Identifying Right Angles in Triangles

right angle

In the above diagram, a is the perpendicular, and b is the base. The side c forms the hypotenuse which is formed at the points (3,5) and (-1,2). The right angle is created at the point (3, -1) where a and b meet.

right angle

If we apply the Pythagorean theorem, ????2 + ????2 = ????2, to find the hypotenuse, ????, with ????=3 and b = 4 units.

????2 = (3)2 + (4)2

    = 9 + 16

    = 25

Therefore,

c = ?25

    = 5

Therefore, the hypotenuse, which is the distance between the two points, can be written as 5 units.

About the Author
Mekhala Joshi

JAIN College

JAIN PU College, a part of the renowned JGI Group, is committed to empowering students with quality education.

Beyond academics, the college ensures its online content reflects the same standard of excellence. Every blog and article is meticulously vetted and proofread by subject matter experts to ensure accuracy, relevance, and clarity. From insightful educational topics to engaging discussions, JAIN PU College's content is crafted to inform, inspire, and add value to its readers, reflecting the institution's commitment to intellectual growth and innovation.

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