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เนื่องจาก AE // BD
̅̅̅̅ ̅̅̅̅
................................................................................................................................................................................
̂
̂
̂
̂
ดังนั้น EAD = ADC = 30° และ EAC = ACB = 60°
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พิจารณา ∆ABD
................................................................................................................................................................................
AB
เนื่องจาก tan 30° =

................................................................................................................................................................................
BD
h
จะได้
................................................................................................................................................................................
tan 30° =

400 + BC
h = (400 + BC) tan 30° ….. 1
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พิจารณา ∆ABC
................................................................................................................................................................................
AB

เนื่องจาก tan 60° =
................................................................................................................................................................................
BC
h
จะได้
................................................................................................................................................................................
tan 60° =

BC
h = BC tan 60°
….. 2
................................................................................................................................................................................
จากสมการ 1 และ 2 จะได้
................................................................................................................................................................................
(400 + BC) tan 30° = BC tan 60°
................................................................................................................................................................................
1
(400 + BC)( ) = BC(√3)
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√3
400 + BC = 3BC
................................................................................................................................................................................
2BC = 400
................................................................................................................................................................................
BC = 200 เมตร
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แทนค่า BC = 200 .ในสมการ 2 จะได้
................................................................................................................................................................................
= 200√3 เมตร
................................................................................................................................................................................
h = 200 tan 60°

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