Online Course Discussion Forum

Winter camp 2018 blue geometry

 
 
Picture of Xin wang
Winter camp 2018 blue geometry
by Xin wang - Sunday, 20 January 2019, 4:21 PM
 

for question 2, e be the midpoint of BC in ABCD, G the intersection of AE and BD, if area of BEG is 1, find area of ABCD

 
Picture of David Reynoso
Re: Winter camp 2018 blue geometry
by David Reynoso - Tuesday, 22 January 2019, 5:28 PM
 

Note $\triangle BGE\sim \triangle DGA$ and the ratio of their sides is $1:2$ (why?) . Use this to find $[ABE]$ in terms of $[BGE]$. Since $B$ is a midpoint, you can also find $[ABE]$ in terms of $[ABCD]$. Combining these two, you can find $[ABCD]$ in terms of $[BGE]$.

The correct answer is $12$.

Picture of Xin wang
Re: Winter camp 2018 blue geometry
by Xin wang - Tuesday, 22 January 2019, 6:07 PM
 

Thank you. Got it now. :)