A school geometry. containing the substance of Euclid books II anfd III and part of book IV (1917)
Hall, H. S. (Henry Sinclair), 1848-1934, Stevens, F. H. (Frederick Haller), 1852-1933 · London : Macmillan · leaf 99
to the ojyposite sides, and the middlepoints of the lines joining the orthocentre to the vertices are concydic. In the A ABC, let X, Y, Z be themiddle points of the sides BC, CA,AB ; let D, E, F be the feet of theperp to these sides from A, B, C ; letO be the orthocentre, and a, ^, 7 themiddle… … X DC 64. And from the A ABO, since BZ = ZA, and BX = XC, .-. ZX is pari to AC. But BO produced makes a rt. angle with AC ; .*. the L XZa is a rt. angle. Similarly, the L XYa is a rt. angle..*. the points X, Z, a, Y are concydic :that is, a lies on the O of the circle which passes through X, Y,…
Geometry
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