-1

I read in my textbook that radian is a constant angle.

What does it mean for an angle to be constant?
Are degree and grade constant angles as well?
What angles are non-constant?

PS : I'm just a beginner in angles, let me know if this is a silly question

Thanks

Rajdeep Sindhu
  • 1,541
  • It means that although the radian is defined in terms of arc length and radius, 1 radian, as an angle, has a constant (fixed) size, like a right angle has a constant size. $\pi \over 2$ radians = 1 right angle. – Peter Phipps Apr 18 '20 at 20:33
  • In many physical applications, an angle varies in time, and hence is not a constant angle. Think of a rotating propeller, for example. – Somos Apr 18 '20 at 21:45
  • @Somos Please check this question out : https://math.stackexchange.com/questions/3760397/what-exactly-is-a-constant-angle – Rajdeep Sindhu Jul 17 '20 at 16:52

1 Answers1

1

If three sides lengths in a triangle are equal then each angle is constant at $60^{\circ}$.

Any angle turned in the plane can be expressed either in degrees or radians.It is a measure of rotation.

If one side is made of thin flexible plastic and you bend it so everywhere it has same distance from the opposite vertex making a circle arc, then the opposite angle reduces by a couple of degrees and a bit more approximately to $57.3^{\circ}$, a famous constant and theoretically useful angle called the radian.

If you take a right or left turn you execute a constant 90 degree angle or $\pi/4$ radian.

And full turn means 360 degrees or $2\pi$ radians.

etc.

Narasimham
  • 40,495