Symud i'r prif gynnwys

460 Old Price's Remains. there waiting for you : nothing as he is, yet he is never nowhere, always everywhere! Definitions 13th and 14th require no remark, except that an angle is not a figure. 15th. Some of my pupils say "by one straight line." Avoid the like : and don't say " straight lines drawn from the centre? before you have learnt what the centre is. 16th. Take the trouble of saying "The point in a circle from which all straight lines drawn to the circum¬ ference are equal." 18th, to be compared carefully with the 19th. If the first line happens to pass through the centre, then the segment is a semi-circle, which is only a particular kind (or "case") of segment. 26th. Observe that two such triangles, whose three sides correspond, may be called mutually equilateral. 27th and 28th. Add to each of these definitions, "and two acute angles," for no triangle has less than two acute angles; so it is only when it has all three acute, that it deserves to be called " acute angled." 30th and 31st. If one angle is a right angle, the rest will be so too. N.B.—The figure of 31st is called rec¬ tangle in Book ii., and both it and 30, 32, and 33, are particular cases of the " Parallelogram." (See proposition 34, note.) 36th. Observe that they never approach ; if they did, they would part on the other side ; and would, at last, come under definition 9th, by forming an angle. Having finished the definitions, we are supposed, my little Friend, to know what Euclid is talking about, to the end of the Book. And there is no shorter way of getting over this, than going through them, again and again if needful, till you do know them, with the aid of sifting questions, and (if you can have the opportunity) hearing the blun-