Kitap 6
33
And it has been proved that, if the circumference BL is in excess of the circumference EN, the angle BGL is also in excess of the angle EHN; if equal, equal; and if less, less.
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Therefore, as the circumference BC is to EF, so is the angle BGC to the angle EHF. [V. Def. 5]
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But, as the angle BGC is to the angle EHF, so is the angle BAC to the angle EDF; for they are doubles respectively.
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Therefore also, as the circumference BC is to the circumference EF, so is the angle BGC to the angle EHF, and the angle BAC to the angle EDF.
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Therefore etc. Q. E. D.
