How should i continue | Mathematics | Page 1

open coral Feb 6, 2023, 10:14 AM

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Should i use the trapezium formula ? To find DFGE

compact jay Feb 6, 2023, 10:19 AM

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open coral

Suppose S(DFGE) = S. Then by the similarity of triangles we have:
S(FCG) = 4S(DCE)
S(ACB) = 9S(DCE)
Moreover:
S(DFGE) = S(FCG) - S(DCE) = 3S(DCE)
Thus, S(DCE) = (1/3)S. So:
S(ABC) = 9S(DCE) = 3S
So, now just substitute S = 2100.

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Not really sure for what purpose AB is given. Oh well.

open coral Feb 6, 2023, 10:21 AM

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is S for area ?

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and what made u put 4 there

ornate girder Feb 6, 2023, 10:29 AM

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open coral is S for area ?

yes

open coral Feb 6, 2023, 10:30 AM

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ornate girder yes

so for S(FCG) = 4S(DCE) how do we know the are of FCG is 4 times DCE

ornate girder Feb 6, 2023, 10:33 AM

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open coral so for S(FCG) = 4S(DCE) how do we know the are of FCG is 4 times DCE

for triangle CDE
let the base = DE = b, and height = h
then S(CDE) = (1/2)bh
CDE ~ CFG
with lengths of CFG twice that of CDE
then S(CFG) = (1/2)(2b)(2h) = 4 * (1/2)bh = 4S(CDE)

open coral Feb 6, 2023, 10:37 AM

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ornate girder for triangle CDE let the base = DE = b, and height = h then S(CDE) = (1/2)bh CDE...

what made u think that the lengths of CFG was twice of CDE

compact jay Feb 6, 2023, 10:38 AM

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Well, since EG = CE, that means CG = 2CE.

#How should i continue