Proving triangles with vector methods

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SUMMARY

The discussion focuses on proving the relationship DE = 1/2BC using vector methods in a triangle where D and E are midpoints of sides AB and AC, respectively. The solution involves expressing the vectors AD and AE in terms of AB and AC, leading to the conclusion that DE equals half of BC. Key corrections were made regarding the signs in the vector equations, emphasizing the importance of maintaining proper vector directionality in calculations.

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Homework Statement



In the following diagram D and E are the midpoints of AB and AC. Use vector methods to prove that DE = 1/2BC

Homework Equations



DE = 1/2 BC

The Attempt at a Solution



AD = 1/2AB
AE = 1/2AC

AD + DE = AE
DE = -AE + AD
DE = -1/2AC + 1/2AD
IF BC = -AC + AB
AND DE = -1/2AC + 1/2AB
THEN 1/2BC = DE
Diagram -
detriangle.jpg
 
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hi crayzwalz! :smile:

yes, that's correct, except …

i] your + and - are the wrong way round in

DE = -AE + AD
and
IF BC = -AC + AB

ii] you should write it all out in one sequence, with the first line

DE =

and the last line

= 1/2BC :wink:
 

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