In the diagram(please see attachment), the exterior angles of triangle ABC are <FAC, <ACD, <ECB, <CBI, <HBA and <BAG. What about the angles <, <DCE, <HBI, are they not exterior?

Printable View

- Jul 16th 2013, 02:51 PMhisajeshExterior angles
In the diagram(please see attachment), the exterior angles of triangle ABC are <FAC, <ACD, <ECB, <CBI, <HBA and <BAG. What about the angles <, <DCE, <HBI, are they not exterior?

- Jul 16th 2013, 03:26 PMPlatoRe: Exterior angles
Look at this webpage.

Note that $\displaystyle \angle GAB$ has a side of $\displaystyle \Delta ABC$, $\displaystyle \overline{AB}$, as a subset.

But $\displaystyle \angle GAH $ has no side of $\displaystyle \Delta ABC$, as a subset. - Jul 16th 2013, 03:28 PMHallsofIvyRe: Exterior angles
The

**definition**of "exterior angle". is "

Exterior Angles of Polygons

"The Exterior Angle is the angle between any side of a shape,

and a line extended from the next side."

http://en.wikipedia.org/wiki/Internal_and_external

"an exterior angle (or external angle) is an angle formed by one side of a simple, closed polygon and a line extended from an adjacent side."

What you have is two "lines extended from adjacent sides". - Jul 16th 2013, 06:04 PMPlatoRe: Exterior angles
This strictly a post script to both of the replies posted.

I have no idea what level we are actually dealing with.

I would like to nail a definition for an exterior angle of a convex polygon.

This is due to R.L.Moore by way of his student Ed Moise in__ELEMENTRY GEOMETY: from an advanced standpoint__.

We need to know what it means that.*two angles form a linear pair*

We say that $\displaystyle \angle XAB$ is an exterior angle if and only if that angle forms a linear pair with an interior of the polygon with vertex $\displaystyle A$