Prove that in Euclidean geometry (so using the 5th postulate) the sum of the angles in a triangle is equal to a straight angle. (For convenience you can use 180° as the measure of a straight angle. As we discussed in class you cannot assume that there is a single, consistent measure for the sum of the angles.)

Elementary Geometry For College Students, 7e
7th Edition
ISBN:9781337614085
Author:Alexander, Daniel C.; Koeberlein, Geralyn M.
Publisher:Alexander, Daniel C.; Koeberlein, Geralyn M.
ChapterP: Preliminary Concepts
SectionP.CT: Test
Problem 1CT
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Prove that in Euclidean geometry (so using the 5th postulate) the sum of
the angles in a triangle is equal to a straight angle. (For convenience you
can use 180° as the measure of a straight angle. As we discussed in class
you cannot assume that there is a single, consistent measure for the
sum of the angles.)
Please try to figure this out rather than looking up a proof online
(though you're welcome to do that afterwards; there are many).
If you get stuck you may want to use the proof above and the diagram
below in which lines AB and CD are parallel:
E
e
B
LL
G
Transcribed Image Text:Prove that in Euclidean geometry (so using the 5th postulate) the sum of the angles in a triangle is equal to a straight angle. (For convenience you can use 180° as the measure of a straight angle. As we discussed in class you cannot assume that there is a single, consistent measure for the sum of the angles.) Please try to figure this out rather than looking up a proof online (though you're welcome to do that afterwards; there are many). If you get stuck you may want to use the proof above and the diagram below in which lines AB and CD are parallel: E e B LL G
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