First principles of Euclid: an introduction to the study of the first book of Euclid's Elements |
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Σελίδα 27
A Rectilineal angle is the inclination ( or B sloping ) of two straight lines towards one another , which meet ( at a point ) ... A C از F B D Thus , to compare the angle BAC with the angle EDF ; apply the angle B A C to the angle EDF ...
A Rectilineal angle is the inclination ( or B sloping ) of two straight lines towards one another , which meet ( at a point ) ... A C از F B D Thus , to compare the angle BAC with the angle EDF ; apply the angle B A C to the angle EDF ...
Σελίδα 28
so that the point A falls upon the point D , and the line A B on the line D E. Then , if the line A C coincide with the line DF , the angles are equal . If the line AC fall within the angle ED F , the angle B A C is less than EDF .
so that the point A falls upon the point D , and the line A B on the line D E. Then , if the line A C coincide with the line DF , the angles are equal . If the line AC fall within the angle ED F , the angle B A C is less than EDF .
Σελίδα 30
Join A F The line A F shall bisect the angle BA C. B D If the angle B A C is bisected by AF ; the angle DAF will be equal to the angle E A F. .. We have to prove that angle DAF equals angle E AF . Proof ( with syllogisms in full ) .
Join A F The line A F shall bisect the angle BA C. B D If the angle B A C is bisected by AF ; the angle DAF will be equal to the angle E A F. .. We have to prove that angle DAF equals angle E AF . Proof ( with syllogisms in full ) .
Σελίδα 31
Wherefore the angle B A C has been divided into the two equal angles BA F , CA F. NOTE . - According to what was said on the definition of an angle ( page 27 ) , angle BAF is the same as DA F ; and angle CA F is the same as E A F Proof ...
Wherefore the angle B A C has been divided into the two equal angles BA F , CA F. NOTE . - According to what was said on the definition of an angle ( page 27 ) , angle BAF is the same as DA F ; and angle CA F is the same as E A F Proof ...
Σελίδα 56
If one side of a triangle be produced , the exterior angle shall be greater than either of the interior opposite angles . Particular Enunciation . Given . ... To prove that the angle ACD is greater than either of the angles ABC or BAC .
If one side of a triangle be produced , the exterior angle shall be greater than either of the interior opposite angles . Particular Enunciation . Given . ... To prove that the angle ACD is greater than either of the angles ABC or BAC .
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Συχνά εμφανιζόμενοι όροι και φράσεις
ABC is equal ABCD angle A CD angle ABC angle B A C angle BAC angle contained angle EDF angles BGH angles equal assumed Axiom Axiom 2a base base B C bisected called centre circle circumference coincide Construction definition describe diameter double draw enunciations of Euc equal angles equal to angle equilateral triangle EXERCISE EXERCISES.-I exterior angle fall figure given point given straight line greater than angle Hence included angle interior opposite angle Join less Let us suppose letters line A B line AB line CD major premiss meet parallel parallelogram Particular Enunciation perpendicular produced Proof proposition prove that angle Repeat Required right angles side A C sides equal square standing Syllogism THEOREM Euclid thing third triangle ABC unequal
Δημοφιλή αποσπάσματα
Σελίδα 83 - If two triangles have two angles of the one equal to two angles of the other, each to each, and one side equal to one side, viz. either the sides adjacent to the equal...
Σελίδα 18 - A circle is a plane figure contained by one line, which is called the circumference, and is such that all straight lines drawn from a certain point within the figure to the circumference, are equal to one another.
Σελίδα 66 - If, from the ends of the side of a triangle, there be drawn two straight lines to a point within the triangle, these shall be less than, the other two sides of the triangle, but shall contain a greater angle. Let...
Σελίδα 34 - When a straight line standing on another straight line makes the adjacent angles equal to one another, each of the angles is called a Right Angle; and the straight line which stands on the other is called a Perpendicular to it.
Σελίδα 94 - Upon the same base, and on the same side of it, there cannot be two triangles that have their sides which are terminated in one extremity of' the base, equal to one another, and likewise those which are terminated in the other extremity.
Σελίδα 88 - THE angles at the base of an isosceles triangle are equal to one another : and, if the equal sides be produced, the angles upon the other side of the base shall be equal.
Σελίδα 104 - If a straight line falling upon two other straight lines, make the exterior angle equal to the interior and opposite upon the same side of the line ; or make the interior angles upon the same side together equal to two right angles ; the two straight lines shall be parallel to one another.
Σελίδα 140 - If the square described upon one of the sides of a triangle, be equal to the squares described upon the other two sides of it ; the angle contained by these two sides is a right angle.
Σελίδα 51 - If, at a point in a straight line, two other straight lines, upon the opposite sides of it, make the adjacent angles together equal to two right angles, these two straight lines shall be in one and the same straight line.
Σελίδα 132 - To a given straight line to apply a parallelogram, which shall be equal to a given triangle, and have one of its angles equal to a given rectilineal angle.