## Elements of Geometry |

### From inside the book

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**angle**; the point of meeting or intersection , A , is the vertex of the**angle**; the lines AB , AC , are its sides . An**angle**is sometimes denoted simply by the letter at the ver- tex , as A ; sometimes by three letters , as**BAC**or CAB ... Page 2

... angles is called a right angle , and the line AB is said to be perpendicular to CD . 11. Every

... angles is called a right angle , and the line AB is said to be perpendicular to CD . 11. Every

**angle BAC**( fig . 4 ) , less than a right angle , is an acute angle ; and every angle , DEF , greater than a right angle , is an obtuse angle ... Page 5

... angles . But , since the angle ACD is a right angle , it fol- lows that its adjacent angle ACE is also a right angle ; therefore the angle ACE = ACD , and AB is perpendicular to DE . 31. Corollary III . All the successive

... angles . But , since the angle ACD is a right angle , it fol- lows that its adjacent angle ACE is also a right angle ; therefore the angle ACE = ACD , and AB is perpendicular to DE . 31. Corollary III . All the successive

**angles**,**BAC**... Page 8

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**angle BAC**, contained by the former , is greater than the angle EDF , contained by the latter ; the third side BC of the first triangle will be greater than the third side EF of the second . Demonstration . Make the angle CAGD , take AG ... Page 9

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**BAC**, then AG + GC < AB + BC ( 41 ) ; therefore , taking away the equal quantities , AG , AB , we shall have GCBC ...**angle**A were greater than the**angle**D , as the sides AB , AC , are equal to the sides DE , DF , each to each , the side ...### Other editions - View all

### Common terms and phrases

ABC fig adjacent angles altitude angle ACB angle BAC base ABCD bisect centre chord circ circular sector circumference circumscribed common cone consequently construction convex surface Corollary cube cylinder Demonstration diagonals diameter draw drawn equal angles equiangular equilateral equivalent faces figure formed four right angles frustum GEOM given point gles greater hence homologous sides hypothenuse inclination intersection isosceles triangle JOHN CRERAR LIBRARY join less Let ABC let fall line AC mean proportional measure the half meet multiplied number of sides oblique lines opposite parallelogram parallelopiped perimeter perpendicular plane MN polyedron prism produced proposition radii radius ratio rectangle regular polygon right angles Scholium sector segment semicircle semicircumference side BC similar solid angle sphere spherical polygons spherical triangle square described straight line tangent THEOREM three angles triangle ABC triangular prism triangular pyramids vertex vertices whence