T H E E L E M E N T S |
Book II Proposition 10 | |
And, since the angle EBC is half a right angle, the angle DBG is also half a right angle. [I.15] But the angle BDG is also right, for it is equal to the angle DCE, they being alternate; [I.29] therefore the remaining angle DGB is half a right angle; [I.32] therefore the angle DGB is equal to the angle DBG, so that the side BD is also equal to the side GD. [I.6] |
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