Question 1063084
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See the lesson <A HREF=https://www.algebra.com/algebra/homework/Angles/Vertical-Angles-.lesson>Vertical angles</A> in this site.



Also, &nbsp;you have this free of charge online textbook on Geometry

&nbsp;&nbsp;&nbsp;&nbsp;<A HREF=https://www.algebra.com/algebra/homework/Triangles/GEOMETRY-your-online-textbook.lesson>GEOMETRY - YOUR ONLINE TEXTBOOK</A> 

in this site.


The referred lesson is the part of this textbook under the topic "<U>Properties of triangles</U>".