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In the triangle above, BD=DC
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Updated on: 28 Mar 2020, 08:03
Updated on: 28 Mar 2020, 08:03
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100% (02:17) correct
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#greprepclub In the triangle above, BD=DC.jpg [ 20.73 KiB | Viewed 1306 times ]
In the triangle above, \(BD=DC\). If \(AD =6\) . What is \(BD \)?
A. 4
B. 6
C. 8
D. 10
E. 12
Show: :: OE
Attachment:
Answer.png [ 149.15 KiB | Viewed 1655 times ]
Re: Triangle Geometry
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04 Jan 2019, 19:14
04 Jan 2019, 19:14
Expert Reply
Hendo21 wrote:
Dear members,
Could anyone help me out with this question? I do not understand why angle BDC = angle BAD + angle DBA. I understand that it is an exterior but it should be equal 180 - angle BDA or? Also I do not understand how they assume that angle BDC (which is 20°) should be 2a. Help would be much appreciated.
Thanks,
Hendo
Could anyone help me out with this question? I do not understand why angle BDC = angle BAD + angle DBA. I understand that it is an exterior but it should be equal 180 - angle BDA or? Also I do not understand how they assume that angle BDC (which is 20°) should be 2a. Help would be much appreciated.
Thanks,
Hendo
Hi..
So, you agree that BDC should be 180-BDA...
Now take ∆BDA...BDA+BAD+DBA=180..sum of angles in a triangle..
Subtract angle BDA from both sides..
BDA+BAD+DBA-BDA=180-BDA.....BAD+DBA=180-BDA...
But BDC is also 180-BDA. Hence BDC=180-BDA=BAD+DBA.
So that is the first query you had...
Yes, as per the figure, we cannot say that angle BAD=angle DBA
But reading into explanation, I feel 20° was meant to be 2a° and there is a typo there.
Re: Triangle Geometry
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05 Jan 2019, 18:31
05 Jan 2019, 18:31
chetan2u wrote:
Hendo21 wrote:
Dear members,
Could anyone help me out with this question? I do not understand why angle BDC = angle BAD + angle DBA. I understand that it is an exterior but it should be equal 180 - angle BDA or? Also I do not understand how they assume that angle BDC (which is 20°) should be 2a. Help would be much appreciated.
Thanks,
Hendo
Could anyone help me out with this question? I do not understand why angle BDC = angle BAD + angle DBA. I understand that it is an exterior but it should be equal 180 - angle BDA or? Also I do not understand how they assume that angle BDC (which is 20°) should be 2a. Help would be much appreciated.
Thanks,
Hendo
Hi..
So, you agree that BDC should be 180-BDA...
Now take ∆BDA...BDA+BAD+DBA=180..sum of angles in a triangle..
Subtract angle BDA from both sides..
BDA+BAD+DBA-BDA=180-BDA.....BAD+DBA=180-BDA...
But BDC is also 180-BDA. Hence BDC=180-BDA=BAD+DBA.
So that is the first query you had...
Yes, as per the figure, we cannot say that angle BAD=angle DBA
But reading into explanation, I feel 20° was meant to be 2a° and there is a typo there.
Very helpful. Many thanks!
