We seldom find out to use the simplest, most organic unit of measure for geometric angles, the revolution (rev). Various other names for this unit are full circle, turn, full turn, and rotation (rot). These space all great names and also they all average the exact same thing.

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1 full circle = 1 rev = 1 turn = 1 rot = 360°


In elementary school, we find out that angles room measured in degrees (°).

1 full circle = 360°

Historical note: The number 360 comes under to united state from antiquity. 360 was valuable to old astronomers since it is around the variety of days in the year. Also, that is useful due to the fact that it is divisible by 2, 3, 4, 5, 6, 8, and 10. Yet the number 360 is arbitrary, no fundamental. If the ancients had characterized the full circle to be part other number of degrees, climate we"d be utilizing that number today.


In high institution trigonometry and calculus classes, we discover that mathematicians like radians (rad).

1 complete circle = 2π rad

Note: If you have actually not yet learned around radians in school, girlfriend may disregard the radians in everything below.

Historical note: The radian was created in the 1700s by mathematicians that wanted to define angles rationally, not using any arbitrary numbers favor 360. They could have rationally defined the complete circle to be 1, yet instead they defined the complete circle to be 2π, the circumference of a one of radius 1. This meaning simplified many equations, specifically equations in ~ the deepest level of mathematics, through removing determinants of 2π. However, it facility many various other equations, specifically equations involving an easy geometry, by introducing components of 2π. The main difficulty with radians is that the base unit, one radian, is awkward: 1 radian = 180/π° = 57.2958°. This is perplexing and also useless for common people. Nobody ever before builds noþeles that has actually an edge of 1 radian, 2 radians, or any kind of integer variety of radians. Unfortunately, mathematicians have deep factors for keeping radians, so we room stuck with them.

Comparing Revolutions, Degrees, and Radians

Let"s compare revolutions and degrees (and radians).


native rev deg rad
no turn 0 0
quarter turn 1/4 90° π/2
half turn 1/2 180° π
three-quarter turn 3/4 270° 3π/2
full turn 1 360°
twelfth turn 1/12 30° π/6
eighth turn 1/8 45° π/4
sixth turn 1/6 60° π/3
fifth turn 1/5 72° 2π/5
third turn 1/3 120° 2π/3
two turns 2 720°
three turns 3 1080°

To transform from transformations to degrees, multiply by 360. To convert from levels to revolutions, division by 360.

When you use levels you are frequently working with integers, but when girlfriend use transformations (or radians) you are often working v fractions (or decimals). Hand calculations are sometimes much easier when you usage revolutions yet sometimes less complicated when you use degrees. It"s good to understand both ways.

Revolutions (turns) room a much more rational and natural unit that measure 보다 degrees. You"ll obtain a deeper expertise of angles if you think about revolutions quite than degrees. An edge is much more fundamentally a subdivision the a circle fairly than a amount of degrees. Because that example, a appropriate angle is more fundamentally a quarter of a circle fairly than a sum of 90 degrees.

Let"s divide the circle right into n equal sectors (see chart below). The edge of every sector is 1/n rev = 360/n° = 2π/n rad. It is easier to understand this if you think around revolutions quite than levels (or radians).


Let"s look in ~ some basic geometry making use of revolutions and also degrees (and radians). The diagram listed below shows supplementary angles, complementary angles, and also triangles. The principles are clearer if you think about revolutions fairly than degrees. The arithmetic may be less complicated using degrees if you have trouble including and individually fractions.


Let"s watch at polygons (see chart below). For a consistent polygon v n sides, the exterior edge is 1/n rev = 360/n° = 2π/n rad. The is easier to know this if girlfriend think about revolutions fairly than degrees (or radians). The interior angle is the complement of the exterior angle.


Teaching Revolutions, Degrees, and also Radians

I think it would be great if teacher would introduce revolutions (turns) in ~ the very same time that they introduce degrees. This will assist the college student to know angles in ~ a more basic level, less dependent top top the arbitrarily magic number 360. Teachers currently introduce the general ide of changes (turns) once they speak things choose "a complete circle is 360°", but they can make the concept an ext numerically an exact by speak "a full turn is 360°, a half turn is 180°, a quarter turn is 90°, and also an eighth turn is 45°" or creating "1 rev = 360°, 1/2 rev = 180°, 1/4 rev = 90°, and 1/8 rev = 45°". Students should occasionally practice doing a few calculations using revolutions (turns) quite than degrees. Of course, student will should spend many of your time learning to calculate with levels (and later, radians), due to the fact that that is the standard.

Angles in Trigonometry and Calculus

Finally, let"s take a fast look at much more advanced mathematics: trigonometry and calculus.

We can consider using transformations with trigonometric functions (sine, cosine, tangent). For example, instead of speak cos(60°) = 1/2 or cos(π/3) = 1/2 making use of radians, we could want come say cos(1/6) = 1/2 using revolutions. However this is not practical since we depend on calculators to advice the trigonometric functions, and calculators frequently have just DEG and also RAD modes, not REV mode.

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When we go to deeper level of mathematics, such together calculus and also mathematical analysis, it transforms out that radians space the many rational and natural units. Because that example, think about this an essential equation: the limit of sin(x)/x as x approaches 0 is precisely 1. This equation would certainly not it is in so elegant if us used any type of unit other than radians.