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Created by: Team Physics - Examples.com, Last Updated: April 25, 2024


What is Radian?

A radian is a unit of angular measurement used in mathematics and physics.A radian is a measure of angle created when the arc length of a circle equals the radius. Essentially, it’s how we measure the bend of a circle using the radius as a guide. One complete circle is about 6.28 radians, equivalent to 360 degrees.

Formula :

One radian = 180/π

Additional Formulas Involving Radian

Arc Length:

L = r × θ

Where L is the arc length, r is the radius of the circle, and θ is the angle in radians.

Area of a Sector:

A = 1/2 r²θ

Where A is the area, r is the radius of the circle, and θ is the angle in radians.

Angular Velocity:

ω = θ/t

Where ω is the angular velocity, θ is the angular displacement in radians, and t is the time.

SI Multiples of Radian

While the radian is a fundamental unit of angular measurement, it doesn’t typically use SI (International System of Units) prefixes like kilo, mega, etc. However, theoretically, they could be applied:

SI PrefixUnit NameMultipleEquivalent in RadiansDescription
KiloradianKiloradian (krad)10³1 kiloradian = 1,000 radiansUsed for larger angular measurements, not commonly employed.
MilliradianMilliradian (mrad)10−³1 milliradian = 0.001 radiansProvides finer precision for detailed measurements.

Conversion of Radian into other Units

To UnitConversion FactorConversion from 10 radians
Degrees (°)1 radian = 57.2958 degrees572.958 degrees
Gradians (gon)1 radian = 63.6620 gradians636.620 gradians
Minutes of arc1 radian = 3437.75 arc minutes34377.5 arc minutes
Seconds of arc1 radian = 206265 arc seconds2062650 arc seconds
Milliradians (mrad)1 radian = 1000 milliradians10,000 milliradians
Microradians (µrad)1 radian = 1,000,000 microradians10,000,000 microradians

Converting radians into other units of angular measurement is a common task in mathematics, physics, and engineering. Here are the key conversion formulas:

From Radians to Degrees:

Conversion :1 radian = 57.2958 degrees 

This formula converts radians to degrees by multiplying the radian measure by 180/π Since 180° is equivalent to π radians.

From Radians to Gradians (gon):

Conversion :1 radian = 63.6620 gradians

From Radians to Minutes of Arc:

Conversion : 1 radian = 3437.75 arc minutes 

Since each degree contains 60 minutes of arc, this formula converts radians to minutes of arc by first converting radians to degrees and then multiplying by 60.

From Radians to Seconds of Arc:

Conversion : 1 radian = 206265 arc seconds

Similar to the conversion to minutes of arc, this formula first converts radians to degrees and then multiplies by 3600 to obtain seconds of arc.

These conversions allow you to express angles in radians in terms of degrees, minutes of arc, or seconds of arc, depending on the desired level of precision.

From Radians to Milliradians (mrad)

Conversion :1 radian = 1000 milliradians

From Radians to Microradians (µrad)

Conversion : 1 radian = 1,000,000 microradians

Difference Between Radian And Milliradian

This table succinctly outlines the distinctions between radians and milliradians, including their magnitudes, approximate conversions, and typical applications.

CharacteristicRadian (rad)Milliradian (mrad)
MagnitudeA unit of angular measurement where one radian subtends an arc length equal to the radius of the circle.One milliradian is equal to one-thousandth of a radian.
Approximate Conversion1 rad = 57.296 degrees1 rad = 1,000 milliradians
Typical ApplicationsMathematical and scientific contexts, calculus, physics, engineering.Ballistics, firearm optics, surveying, where precise angular measurements are required.

Uses of Radian

Uses of Radian

Radians are extensively used in various branches of physics due to their natural relationship with circular motion and angles. Some key applications include:

1. Rotational Motion: Radians are crucial for describing the angular displacement, velocity, and acceleration of rotating objects. In mechanics, rotational kinematics and dynamics equations are often formulated in terms of radians to represent the angle of rotation.

2.Simple Harmonic Motion: Many oscillatory systems, such as pendulums and springs, undergo simple harmonic motion. Radians are employed to measure the phase angle and angular frequency of these oscillations, facilitating the analysis and prediction of their behavior.

3.Wave Phenomena: Radians play a fundamental role in describing wave phenomena, including wave propagation, interference, and diffraction. Angular measures are utilized to express phase differences between waveforms and to calculate wave parameters like wavelength and wave vector.

4.Electricity and Magnetism: In alternating current (AC) circuits, radians are used to quantify phase differences between voltage and current waveforms. Phasors, which represent sinusoidal quantities, are often expressed in radians to simplify calculations in circuit analysis.

5.Quantum Mechanics: In quantum mechanics, radians are employed to describe the phase of wavefunctions, which represent the probability amplitudes of particles. The phase angle plays a crucial role in determining interference patterns and probability distributions in quantum systems.

6.Astrophysics:Radians are utilized in astrophysics to measure angular distances and sizes of celestial objects, such as stars, galaxies, and planetary orbits. Angular measures are essential for determining positions, motions, and dimensions in the vastness of the universe.


Why do we use radians instead of degrees in calculus and physics?

Radians are preferred in calculus and physics because they simplify many mathematical formulas and relationships.

How do radians relate to circular motion?

In circular motion, radians are used to measure angles as objects rotate around a center point. The angle in radians represents the fraction of the circle that has been traversed by the rotating object.

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