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In triangle $ABC$, let the perpendicular bisector of $BC$ intersect $BC$ and $AC$ at $D$ and $E$, respectively. If $BC = 20$ and $\angle C = 15^\circ$, then find the length of $BE$.

 Nov 17, 2024
 #1
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Let's graph (yay!)

 

What's interesting about this is this is on a coordinate plane, so we can make quite a few deductions from it. 

First off, we have that

CD=BD=10ED=ED

 

Also though, note that ED and BC are just the x and y axis, thus they are perpendicular lines. 

Which means that we have CDE=BDE

 

By SAS Congruence, we know that triangle CDE is congruent to triangle BDE.

Thus, we can conclude that corresponding sides CE=BE

 

Finally, we just simply right that

sinCED/CD=sinCDE/CEsin75/10=sin90/CECE=10sin75=BE10.35

 

Thus, 10.35 SHOULD be correct, not sure, trig is never my thing :(

 

Thanks! :)

 Nov 18, 2024
edited by NotThatSmart  Nov 18, 2024

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