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## Algebra 2

### Course: Algebra 2>Unit 11

Sal discusses the general approach to converting between radians and degrees and vice versa. Created by Sal Khan.

## Want to join the conversation?

• Can you possibly have negative angles? •   Negative angles are clockwise angles. (Counterclockwise is positive)
• If pi continues forever, how can we use it to define answers? That would mean every answer we get would continue on forever, but we shorten pi and thus makes none of the math we do with pi actually 100% true but rather an estimated amount. I don't even understand the concept of pi honestly. Can someone explain to me? •  Take a measurement of a length of anything, we won't get an exact whole number. A pencil said to be 8 cm long may be 8.000034 cm for example. We are always estimating because the exact amount is almost never needed, and we take as accurate a measurement as required. So, every answer may continue on forever, but what we estimate, is what we need practically.

Theoretically in math, since we always use rational numbers most of the time, an irrational number like pi is often confusing as it does not provide a definite rational answer. Instead we have to estimate to the accuracy required for the situation. If you want to find the circumference of a random cart wheel, you dont need accuracy. When you find the circumference of a rocket, you may need more accuracy.

But of course, theoretically we can still get a definite answer if we just dont expand π and leave it as π. Circumference of a circle of diameter 3 is 3π. This gives you a perfect theortical answer. Otherwise it would be 3*3.14..... and as you said, it is not a perfect defined answer and is not theoretically accurate.

Hope this helps!
- Super7SonicX
• Is there any kind of notation for radians? •  Yes, there is, though it is rarely used.
You write degrees with a little circle at the top 1.2°
Same way, an angle of 1.2 radians would be written either as "1.2 rad" or "1.2 with a "c" at the top.(I can't seem to get the 'c' using formatting here.)

See-
• Are negative degrees actual things, or are they hypothetical like negative numbers? • Is there any other way to measure the angle just like degrees, radians....? • Is 1.5 pi the same as 270? • Why did humans invent radians and degrees? Isn't one enough? • When I have 5pi/9 and I am converting it to degrees do I set them up in the proportion just as in the video? And just like the example with -pi/2 do I multiply the 5 by 180? My answer was 100 degrees. Would like to know if I did it right. thx!!   