| | | GEO0004 -- Thales' Theorem |
Theorem. [Thales' Theorem] At intersecting sides of an angle ∠ BOD by parallel lines BD and AC, the angle sides are divided into the proportional segments: (OA)/(OB) = (OC)/(OD)
point O 40 10
point A 80 10
point C 60 30
online B O A
line a A C
line c O C
parallel b B a
intersec D c b
drawline O A
drawline O C
drawline A C
drawline B D
cmark_t O
cmark_t A
cmark_t B
cmark_t C
cmark_t D
% parallel BC' and B'C
prove { equal { sratio O A O B } { sratio O C O D } }
| | | GEO0004 -- Thales' Theorem |