|  |  | GEO0004 -- Thales' Theorem

## GEO0004 -- Thales' Theorem

##### The Theorem Statment

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)

##### The Image - GCLC 5.0

##### Prover's Code

    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  } }

##### Proved -- Proof, made with GCLC, v1.0

proofGEO0004.pdf

|  |  | GEO0004 -- Thales' Theorem