Geometry question

[KBKMNN]

Yes, it's me once again with a math question, only it isn't fractions this time. This is a little complicated (especially for my brain) so I hope y'all will understand what I'm trying to ask.
I got a protractor for my son yesterday since we are trying to measure angles. I just got a cheap one and it has two rows of numbers. The bottom row goes from 180 on the left side, to 180 on the right side. And the top row goes from 0 to 0. I get the basic idea of how to measure an angle. I know a circle is 360 degrees and a straight line would be 180, and I know what a 90 degree angle looks like, and what a 45 degree one looks like and so on. My question is, how does one differentiate between a, let's say 30 degree angle as opposed to it being 150 degrees? So like on the protractor the number 150 is on top of the 30. How do I know if the angle is 150 or 30?
Does it all depend on which way the angle is facing, like the open end on the left side or the open end on the right side. They're all considered right angles, right? (pun intended) :heh
Am I clear as mud? :hehee

[Wally]

Typically you establish an x-y plane or mark the angle to be measured by a small semicircle usually with the degree mark and a ? mark.


If using x-y axis you normally have zero going to the right and everything is measured counter-clockwise from it. Straight up woud be 90.

However some angles are measured from the x axis [horizontal line] with angles above in positive numbers and ones below in negative numbers but still using the line to the right as the zero reference point.


If using it for ship or airplane directions, then straight ahead is zero and angles are measured as degrees starbord or degrees port.
Straight ahead is also 12 o'clock for aircraft hence the term; check your six (o'clock) - look behind you.



Does this help?

[NoTomorrow]

Your protractor should go from 0 to 180 in both directions. Think of an angle as a mouth opening. A mouth that is opened a little could measure 30 degrees. The wider it opens, the bigger it gets. So, when it opens to 90 degrees, it is a right angle, a very nice corner. When it opens up past 90 degrees, then the numbers continue to get bigger. So, a 150 degree angle is one that is opened very wide, an obtuse angle, much like one of those chairs you lay out on by the poolside.

The reason for the second set of numbers is in case your angle is facing in the opposite direction. You might check out books like Math On Call or Geometry To Go that are great books for when you just need to look up something about math.

[KBKMNN]

Your protractor should go from 0 to 180 in both directions. Think of an angle as a mouth opening. A mouth that is opened a little could measure 30 degrees. The wider it opens, the bigger it gets. So, when it opens to 90 degrees, it is a right angle, a very nice corner. When it opens up past 90 degrees, then the numbers continue to get bigger. So, a 150 degree angle is one that is opened very wide, an obtuse angle, much like one of those chairs you lay out on by the poolside.

The reason for the second set of numbers is in case your angle is facing in the opposite direction. You might check out books like Math On Call or Geometry To Go that are great books for when you just need to look up something about math.


Yes, you're right. I apparently wasn't looking at the protractor correctly. It's just on one side the 0 is on the bottom and the 180 is on top and on the right side vice versa.
Thanks for the help. :hat

[Reason&Hope]

Just to summarize, acute angles are less than 90 degrees. So, if your angle is acute and it's pointing at the 30/150 line, then it must be 30 degrees. If your angle is obtuse and pointing at the 30/150 line, then it must be 150 degrees.

[KBKMNN]

Just to summarize, acute angles are less than 90 degrees. So, if your angle is acute and it's pointing at the 30/150 line, then it must be 30 degrees. If your angle is obtuse and pointing at the 30/150 line, then it must be 150 degrees.

Like I said, I understand the basics. I know acute and obtuse, but I just didn't understand how it worked. (I'm just clarifying that so you all don't think I'm a total idiot) :hehee You put it very succinctly for me. I get it now! Thanks! :hat

[Pendragon]

Just to summarize, acute angles are less than 90 degrees. So, if your angle is acute and it's pointing at the 30/150 line, then it must be 30 degrees. If your angle is obtuse and pointing at the 30/150 line, then it must be 150 degrees.
I once enjoyed having a 190 degree ange but yet I found out it was just a cute 10 degree angle with a very obtuse 170 degree angle haning onSo I put it on a diet and now it is square at just 90 degrees

[KBKMNN]

I once enjoyed having a 190 degree ange but yet I found out it was just a cute 10 degree angle with a very obtuse 170 degree angle haning onSo I put it on a diet and now it is square at just 90 degrees

:rotfl Just what I needed tonight! :lol2 Thanks for the laugh.