Prove that the perpendicular bisector of the hypotenuse of 30∘−60∘−90∘ triangle divides the larger leg into two parts having the ratio 2:1.
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Solution
Let the hypotenous = AC = h ∴AE=EC=h2 ∵ DE is the perpendicular bisector) In ΔDEA DEAE=tan30=1√3 DE=AE√3=h2√3 DEAD=sin30 AD=DEsin30=h2√312 =h√h In ΔDEC Let ∠DCE=θ ∴tanθ=DEEC=h2√3×1h2 =1√3 ⇒θ=30∘ ∴∠DCE=∠DCB=30∘ sin30=DEDC=h2√3DC=12 DC=h√3 In ΔDCB sin30=DBDC 12=DBDC⇒DB=DC2=h2√3 ∴ADDB=h√3h2√3=21=2:1