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July 18th, 2017, 07:24 AM  #1 
Newbie Joined: Jul 2017 From: Denmark Posts: 11 Thanks: 0  Similar triangles with scale factor sqrt 3
Hi! You have triangle ABC. On BC there's a point, D. AD splits ABC into two similar triangles (uniform triangles?) hence ABD~ACD. The scale factor is sqrt 3; what are the sizes of the angles in ABC? Last edited by skipjack; July 18th, 2017 at 08:59 AM. 
July 18th, 2017, 09:30 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 18,707 Thanks: 1532 
If $\small\triangle$ABD ~ $\small\triangle$CAD, they want you to find 30$^\circ\!$, 60$^\circ\!$ and 90$^\circ\!$.

July 19th, 2017, 01:57 AM  #3 
Newbie Joined: Jul 2017 From: Denmark Posts: 11 Thanks: 0  How?
Okey! But how do I find those angles?

July 19th, 2017, 02:10 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 18,707 Thanks: 1532 
Angles BDA and ADC are equal, so they are both 90$^\circ\!$. Hence angle BAC is also 90$^\circ\!$. Can you make progress from there? 
July 19th, 2017, 11:17 AM  #5 
Newbie Joined: Jul 2017 From: Denmark Posts: 11 Thanks: 0 
But who says that BD=DC? Bc if angles BDA and ADC are equal, the scale factor will be 1, right? As AD will be the same side in both triangles. And further on, if BDA and ADC are equal, it will split BC in two equal parts, hence scale factor 1 again. Or? 
July 19th, 2017, 10:59 PM  #6 
Global Moderator Joined: Dec 2006 Posts: 18,707 Thanks: 1532 
I didn't assert that BD = DC. One is 3 times the other.


Tags 
factor, scale, similar, sqrt, triangels, triangles 
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