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In triangle ABC, AB is larger than BC.

Then, we choose point E outside the triangle such that BE=BC.

We extend line AB to D, such that BD=BC.

BF is angle bisector of angle ABC.

If DC is parallel to BF, what is the measure of angle ECD?

akusaja
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  • Could you provide a picture or something ? I tried drawing the triangle step by step until I stepped on the last line and figured out the triangle could not be any triangle – T_O Mar 25 '14 at 19:19
  • What do you mean "if DC is parallel to BF"? DC is parallel to BF by corresponding angle theorem! In my view this question needs a little rewording – imranfat Mar 25 '14 at 19:19
  • I've tried to draw it. Here's my image: http://i61.tinypic.com/24qtjeg.png – akusaja Mar 25 '14 at 19:28

1 Answers1

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According to your drawing, the angle ECD is equal to the angle CBF, and the latter is half of the angle ABC.

All in all :

$$\hat{ECD}=\hat{ABC}/2$$

If you don't have any information on the angle ABC, then you wont find the angle ECD

T_O
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