Math Is Fun Forum

post the question and your answer here please.

Bob

Hi Milenne and jabah013.307

I too cannot figure out what you are after. 

jabah: from your Ip it looks like you're in the UK.  I've checked the government website and reflex angles are not in the year 4 programme of study.  Simple identification questions like " Is this angle acute, obtuse or reflex?" come in year 5.  Of course it's possible the US curriculum has this a year earlier but even so it's not a topic to get worried over.

Get a piece of paper and mark a point O as the centre of a circle and also put on a fixed point A. Now have a second point B that can freely roam around the circle.

If B is on top of A the angle AOB is zero.

If C is the point where COA = 90 then when B is between A and C the angle AOB will be acute (ie. less than 90)

If D is the point where AOD makes a straight line (the diameter of the circle) then any position for B between C and D make AOB on obtuse angle ie between 90 and 180.

If B moves even further around the circle then AOB will be reflex ie. over 180.

That is until B is once more on top of A.  We could call the angle AOB 360 in that case but it's the same as zero.  As B continues to rotate around the circle the angle goes over 360.  eg. 370.  But we don't have a special name for such angles as 370 looks the same as 10.

So the words acute, obtuse and reflex are just names given to different groups of angles.

On a protractor there are usually two scales, one running clockwise and the other anticlockwise.  So one way it's 0 to 180 and the other way it's 180 to 0.

This gives the user the option to measure an angle clockwise or anticlockwise.  You can get 360 protractors so you could measure a reflex angle with one of these.  But you don't really need such a protractor as it's easy enough to add 180 to your measurement.

Milenne wrote:

how can you find the reflex angles of angles that are also reflex?

This question doesn't make sense.  Reflex is just a describing word (like heavy or blue but for a type of angle) so you cannot find the reflex angle of anything any more than you can find the 'heavy' of something or the 'blue' of something.

So it looks like we have a translation issue here, and that's not what you mean.  I googled reflex angles and there are loads of worksheets available.  So if you are having trouble putting up a diagram, how about giving us the link to a worksheet that has a similar problem.

At the moment that's the most help I can offer.

Bob

Hi! I have been finding websites to find out the answer to this and finally, it came! Anyway, how can you find the reflex angles of angles that are also reflex? I know that this is a bit complicated to answer, but my math teacher said that this was a part of a year 4 math test but I am in year 8! Even my classmates said that this was so complicated.

And one of my other friends has a pair that tell her left and right.

I have a pair that tells me whether they are clean or not.