Math Is Fun Forum

alainlegrand

Member

Registered: 2012-06-23

Posts: 2

Building a triangle ?

HI! Little question here :

IS it possible to do build a triangle with only 3 angles known ? And how do you do it ? I searched on google and it gave nothing... please help ! Thanks ! A link would be good !

*DO I only do angles with my protractor without any technique ? Or is there a specific way of doing it ? Just to be sure it's the correct way !

Last edited by alainlegrand (2012-06-23 06:23:34)

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Building a triangle ?

You can, but there isn't only one such triangle. There are infinitely many triangle with three angles given.

Actually, you don't even need all three angles, you need only two. What you can do is draw any line segment. Then you draw the two angles given on the ends of that line segment and see where they intersect. That will be the third point of the triangle.

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“Here lies the reader who will never open this book. He is forever dead.
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alainlegrand

Member

Registered: 2012-06-23

Posts: 2

Re: Building a triangle ?

ok thanks! That's what I did anyway because I though there was a special way with the compas or something like that ! Thanks again

Bob

Administrator

Registered: 2010-06-20

Posts: 10,582

Re: Building a triangle ?

hi alainlegrand

Welcome to the forum.

For most angles you need a protractor.  You can do 90 and 60 with a ruler and compass and then bisect them, again with just ruler and compass.

The place to look is

http://www.mathsisfun.com/geometry/constructions.html

The animations here make these really clear.  Just click on the underlined words to see how to do the construction.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob