Can a straight line be divided in the ratio by using only compass and straightedge?
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Since ( 2 − 3 ) : ( 2 + 3 ) = 1 : ( 7 + 4 3 ) , we're looking to construct 1 + ( 7 + 4 3 ) 1 = 8 + 4 3 1 = 4 1 ( 2 − 3 ) of a line segment. Since this is a constructible number, the answer is yes .
One example construction: Call our line segment A B .
Proving it is easy. Treat A B as having 4 units length. Then A D = D C = 4 1 A B = 1 . Also, D E = D A = 1 , so C E = C F = 2 . Since A B is perpendicular to both D E and F G , the latter two are parallel. Since A B is parallel to E G , D E G F is a rectangle, so F G = D E = 1 . Thus C G = C H = 3 . So A H = 2 − 3 , and by subtraction, H B = A B − A H = 2 + 3 .