Help with 2 9th grade geometry questions

N

negevasaf

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Feb 1, 2015
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Update: I solved the 1st question.
I had two questions I couldn't solve:
Do you think you can help? Thank you.
 
Last edited:
negevasaf said:
I had two questions I couldn't solve:
Do you think you can help? Thank you.
Click to expand...
What are your thoughts? What have you tried? How far have you gotten? Where are you stuck?

For instance, for the first question, one can use vertical angles and the marked sides to create congruent triangles ADC and EDB, from which the first result follows immediately. (I'm not familiar with the S-sub-delta notation, so I cannot comment on that.)

Please be complete. Thank you! :wink:
 
stapel said:
What are your thoughts? What have you tried? How far have you gotten? Where are you stuck?

For instance, for the first question, one can use vertical angles and the marked sides to create congruent triangles ADC and EDB, from which the first result follows immediately. (I'm not familiar with the S-sub-delta notation, so I cannot comment on that.)

Please be complete. Thank you! :wink:
Click to expand...
Okay I read the forum rules, and I already solved question 1.
But I have no idea what to do in the 2nd question, I got nothing.
Can you please help me to start?
Thank you.
 
negevasaf said:
I have no idea what to do in the 2nd question, I got nothing.
Can you please help me to start?
Click to expand...
Can you please reply with the requested notational definition? Thank you! ;)
 
negevasaf said:
S means area, I need to prove that triangle ABC area is equal to triangle ADC.
Click to expand...
Consider triangles DEC and BEC, with DB containing the bases for each. Draw the perpendicular from C to DB; this is the height. Now what can you say about the areas of these two triangles?

Do the same sort of thing with triangles ADE and ABE. What can you conclude about their areas? What then can you conclude about the sums of areas? ;)
 
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