New Topic
GeoGebraTopicProblemEnglish
This object is in archive! 
Properties
Category English
Tags geometry, angles, calculation
Similar Topics
Statistics
Comments
4
Participants
3
Subscribers
26
Votes
1
Views
1035

Angle calculated 135° instead of 136° Geogebra Classic 6

Kharlamov Konstantin shared this problem 5 years ago
Not a Problem

This does not seem to be a rounding error, because the actual angle is 136.028°, so if it get rounded, it would be in between 136..137. The correct angle can be quickly calculated e.g. with this online calculator https://www.triangle-calcul... (but I found the error for writing a test case for a function calculating an angle for my car bot).Steps to reproduce:

1. Press button "Create angle", and place it to points A=(1,0), B=(0,0), C=(-1,1), (as in illustration) (I had to place screenshot here https://imgur.com/a/O6FwH because site complains "path not found at" for images uploaded locally — I guess there's some silly timeout — deleting and reuploading the image doesn't help, and using a link doesn't do any better either).

Expected: the angle shown is 136°

Actual: the angle shows 135°

Additional info:

Geogebra version: 6.0.414.0-offline

OS: Archlinux.

1 The same problem

Comments (4)

photo
1
Simona Riva ● 5 years ago

The angle IS actually 135°.

Please note that line OC is the bisector of the 2nd and 4th quadrant of the plane.

Reply
photo
1
Kharlamov Konstantin ● 5 years ago

Then why calculations using lengths consistently getting 136°?

photo
1
Simona Riva ● 5 years ago

Because you are probably entering in that site the approximate values for the length of sides instead of exact ones.

Use trig, or if you don't know it, use the Pythagoras theorem to obtain the exact values of the sides.

Exact means e.g. sqrt(2) instead of 1.41

photo
1
Hanka Chrenkova ● 3 years ago

I think the angle is 135 deg. I calculated it from vertex coordinates using the tool:

https://www.triangle-calcul...


Sides are sqrt(2) and sqrt(5). If you round these sides to hundreds, you lose some precision and angles are different.

photo
Leave a Comment
 
Attach a file
© 2023 International GeoGebra Institute