00:01
Okay, you are told that a circle of radius 2 .5, subtends an arc length of 7 centimeters, as shown here.
00:11
I want to work out theta in degrees and in radiance.
00:16
Well, theta out of 360 is the fraction of the circle in degrees times 2 pi r, so 2 .5, has to equal 7, means then that theta must be 7 times 360 divided by phi.
00:43
And that i work out, 7 times 360, divide that by 5, divide that by pi, and i get 160 .43 degrees.
01:02
And here they want what accuracy, doesn't say.
01:07
Okay.
01:07
Okay, so that's the first bit then.
01:12
Now to find it in radiance, very straightforward, there's a formula, arc length s equals r times theta in radiance...