Basic proportionality theorem (Thales)
Plane geometry · Mathematics
Study notes
Q: In △ABC, D on AB with AD = 4, DB = 6; DE || BC meets AC at E with AE = 6. Find EC. AD/DB = AE/EC: 4/6 = 6/EC. EC = 6×6/4 = 9. Check: 4/6 = 2/3, 6/9 = 2/3 ✓!
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Plane geometry · Mathematics
Q: In △ABC, D on AB with AD = 4, DB = 6; DE || BC meets AC at E with AE = 6. Find EC. AD/DB = AE/EC: 4/6 = 6/EC. EC = 6×6/4 = 9. Check: 4/6 = 2/3, 6/9 = 2/3 ✓!