## An Introduction to Geometry and the Science of Form: Prepared from the Most Approved Prussian Text-books |

### From inside the book

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**protractor**, ( fig . 55 , ) which is an instrument used in plotting , that is , drawing upon paper angles whose magnitude is known ; or for meas- uring angles already drawn upon paper . It is a semi- circle of wood , metal , or horn ... Page 57

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**Protractor**. It is required to make a right angle at the point O in the straight line AB , ( fig . 48. ) Apply the diameter of the**protractor**to the given line so that the centre shall fall exactly on the point O. Mark on the paper the ... Page 58

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**protractor**. Mark on the paper the point where the centre of the**protractor**lies , and also the point where the given number of degrees on the arc of the**protractor**lies . Connect these two points by a straight line , and the required ... Page 59

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**Protractor**. Measure the number of degrees in the given angle , and then make an angle of the same number of degrees . Sol . 2. With the Compasses . Draw the straight line CD . From O as a centre , with any radius , describe an arc ... Page 79

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**protractor**. For measuring angles in the field various instruments are used , more or less compli- cated . The most simple is a graduated circle , ( which may be made of metal , wood , or pasteboard , ) with an index moving on a pivot ...### Other editions - View all

### Common terms and phrases

adjacent angles angle BAC angles are equal Bisect centre chord circumference coincide concave angles consequently angle construct a square convex angle convex surface cube curved line cylinder decagonal describe a circle diagonals diameter divided division points draw a line Draw a straight equal altitude equal angles equal bases equivalent erect a perpendicular exterior angles feet found by multiplying given number given square greatest number hexagon homologous sides hypothenuse inches inscribed circle isosceles triangle length let fall line drawn line passes magnitude measured Multiply the number number of lines number of points number of straight opposite parallelogram parallelopiped passes 2 points pendicular pentagon proportion protractor quadrilateral radii radius equal ratio regular polygon right angle semi-circumference set intersecting side AC similar similar triangles solidity sphere straight line suppose tangents triangle ABC triangular prism unequal vertex vertices

### Popular passages

Page 130 - The first and fourth terms of a proportion are called the extremes, and the second and third terms, the means. Thus, in the foregoing proportion, 8 and 3 are the extremes and 4 and 6 are the means.

Page 154 - In a series of equal ratios, any antecedent is to its consequent, as the sum of all the antecedents is to the sum of all the consequents. Let a: 6 = c: d = e :/. Then, by Art.