Question 1068287
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<pre>
m < CAB  +m < CBA  = 180 - m < c.


m < C is the same for all positions of the point C in the circle and is half of the measure of the arc AB, 
      since the angle C is an inscribed angle.


It implies that  m < CAB  +m < CBA  = const,
</pre>

QED.


On inscribed angles see the lesson

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Circles/An-inscribed-angle.lesson>An inscribed angle in a circle</A>, 

in this site.



Also, 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 circles, inscribed angles, chords, secants and tangents</U>".