## Elements of Geometry |

### From inside the book

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**adjacent**angles BAC , BAD , are equal , each of these 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 ... Page 3

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**adjacent**, as AC ( fig . 42 ) . 19. An equilateral polygon is one which has all its sides equal ; an equiangular polygon is one which has all its angles equal . • 20. Two polygons are equilateral with respect to each other , when they ... Page 4

... straight line CD ( fig . 17 ) , which meets another straight line AB , makes with it two

... straight line CD ( fig . 17 ) , which meets another straight line AB , makes with it two

**adjacent**angles ACD , BCD , which , taken together , are equal to two right angles . Demonstration . At the point C , let CE be PART FIRST. ... Page 5

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**adjacent**angle DCB , and that they are both right 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 ... Page 6

Adrien Marie Legendre. THEOREM . Fig . 2 33. If two

Adrien Marie Legendre. THEOREM . Fig . 2 33. If two

**adjacent**angles ACD , DCB ( fig . 20 ) , are together equal to two right angles , the two exterior sides AC , CB , are in the same straight line . Demonstration . For if CB is not the ...### 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