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# Geometry Problem:

+3
58
3
+374

Geometry Problem:

May 24, 2021

#1
+25928
+5

Geometry Problem:

$$\text{Let the side of the square = a. AD=DC=a } \\ \text{Let DF = y } \\ \text{Let the area of triangle [AED]=\dfrac{a^2}{2} } \\ \text{Let the area of triangle [BCF]=\dfrac{(a-y)a}{2}=S_2+S_4+S_7 } \\ \text{Let the area of triangle [ADF]=\dfrac{ay}{2}=S_5+S_8 }$$

$$\begin{array}{|rcll|} \hline \dfrac{(a-y)a}{2} &=& S_2+S_4+S_7 \\ \mathbf{S_4} &=& \dfrac{(a-y)a}{2} - S_2 - S_7 \\ \hline \dfrac{ay}{2} &=& S_5+S_8 \\ \mathbf{S_5} &=& \dfrac{ay}{2} - S_8 \\ \hline \mathbf{S_3} &=& \mathbf{[AED] - S_4 -S_5} \\ S_3 &=& \dfrac{a^2}{2} -\left( \dfrac{(a-y)a}{2} - S_2 - S_7 \right) - \left(\dfrac{ay}{2} - S_8 \right) \\ S_3 &=& \dfrac{a^2}{2}-\dfrac{a^2}{2} +\dfrac{ay}{2} + S_2 + S_7 - \dfrac{ay}{2} + S_8 \\ S_3 &=& S_2 + S_7 + S_8 \\ S_3 &=& 2 + 8 + 2 \\ \mathbf{S_3} &=& \mathbf{12} \\ \hline \end{array}$$

May 25, 2021
#2
+1318
+1

Excellent work, heureka!!! Can you find the length of a?

civonamzuk  May 25, 2021
#3
+1796
0

That's so smart.

I understand how you did it, but how did you figure out to use that method?

=^._.^=

catmg  May 25, 2021