Geometry Negative Angles
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Unwind
Negative Angles

 

 OK, in the last example on the last page we had:

 

 450 degrees = 90 degrees

 
 That means we can also subtract 360 degrees from any angle
 and be right back where we started.
 
 When we subtract angles,
 we go in the other direction.
 That is, the direction the clock actually moves ...
 
 So 450 degrees minus 360 degrees equals 90 degrees
 looks like this:
 

 

 
 We can subtract angles other than full 360 degree circles.
 
 We could start with a 90 degree angle:
 

 

 
 and subtract 180 degrees ...
 

 

 
 So watch closely ...
 

 

 
 This trip into negative numbers is no big deal ...
 

 270 degrees - 360 degrees = - 90 degrees

 

- 90 degrees + 360 degrees = 270 degrees

 

   copyright 2005 Bruce Kirkpatrick

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