# Construct an angle

• Jun 5th 2010, 11:36 AM
Mukilab
Construct an angle
A question tells me to construct an angle using a ruler and a pair of compasses.

No idea how to do this without a protractor, any help?
• Jun 5th 2010, 01:12 PM
Quote:

Originally Posted by Mukilab
A question tells me to construct an angle using a ruler and a pair of compasses.

No idea how to do this without a protractor, any help?

Compass and straightedge constructions - Wikipedia, the free encyclopedia
• Jun 6th 2010, 12:39 AM
Mukilab
Doesn't tell me how to create an angle using only a ruler and compass
• Jun 6th 2010, 03:10 AM
Mukilab
Any other help?

I've thought about this and I don't know how it can be feasibly possible without extensive working and no calculator.

Surely there must be some error because you can simply do this with a protractor and ruler. :(
• Jun 6th 2010, 04:22 AM
Quote:

Originally Posted by Mukilab
Any other help?

I've thought about this and I don't know how it can be feasibly possible without extensive working and no calculator.

Surely there must be some error because you can simply do this with a protractor and ruler. :(

Isn't it amazing that the link shows a few being constructed then...

Which angle are you trying to do.
• Jun 6th 2010, 07:36 AM
Mukilab
I have a single line. From that single line I am supposed to construct an angle of 30 degrees.
• Jun 6th 2010, 07:52 AM
How to construct (draw) a 30 degree angle with compass and straightedge or ruler - Math Open Reference

Or construct a equilateral triangle using the wiki link and figure out how to divide an angle in two...

These take a bit of time to explain so google is the best bet.
• Jun 6th 2010, 08:12 AM
Mukilab
thanks, there are so many new things on that site. I wonder how these can be proved without measurement.
• Jun 6th 2010, 08:42 AM
hungthinh92
Actually, if you want to find 30 degree angle with compass and ruler, you can do like this:
A. Draw an equilateral triangle:
Step 1: Draw a random line.
Step 2: Put the point of your compass at one end of the segment and the pencil point at the other.
Step 3: Without moving the point of the compass and without changing how wide it is set, swing the compass in approximately a quarter-circle (up & away from the line segment).
Step 4: Without changing how wide the compass is spread, move the compass point to the other end.
Step 5: Swing the compass so that the arc you are creating crosses the arc you drew in step 3.
Step 6: Mark the place where the two arcs cross.
Step 7: Using a ruler, draw line segments that connect the spot where the arcs cross to each end of the original line segment.
B. Draw a height of the triangle.http://mathcentral.uregina.ca/QQ/dat...9.02/rosa2.gif