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I'm not sure if I understand this question right.

Q. Given an angle at a point A and given another segment BC, construct a point D so that the angle DBC equals the given angle at A.

Figure - Question Figure

Should I assume one of the sides of the angle a is bc and the end point of the other side is the point d ?

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Not quite. One of the sides of the reproduced angle is $bc$, and the endpoint of the other side is $d$. –  David Mitra Jan 30 '13 at 17:28
    
@DavidMitra - I might be misinterpreting what you said, but how is that different from what I intended on assuming ? –  devcoder Jan 30 '13 at 17:52
    
I may be misinterpreting you. It seemed you wanted to take angle $a$ and just call one of its sides $bc$. You have to, of course, reproduce the angle on the line segment $bc$ as given. (The reproduced angle has to be called something other than "$a$"). –  David Mitra Jan 30 '13 at 17:56
    
@DavidMitra - You are right. But I am still confused on how to reproduce the angle a on the line segment bc? –  devcoder Jan 30 '13 at 18:03
    
Hint: 1) Draw an arc, with arbitrary radius, on angle $a$ with center the vertex of $a$. Call the points of intersection of $a$ and the arc $e$ and $d$ . 2) Draw an arc of radius $d$ with center $b$ on the segment $bc$ 3) How could you find the points on the arc drawn in 2) that correspond to the points $d$ and $e$? –  David Mitra Jan 30 '13 at 18:07

1 Answer 1

up vote 1 down vote accepted

David Mitra was spot on. Go the the following link it has the proof and a java video to help you understand. Are you in Math430 UMD?

http://www.mathopenref.com/constcopyangle.html

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