Construction / Practical Geometry (basics) : Geometrical Instruments

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Geometrical Instruments

what you'll learn...

overview

In this page, overview of the geometrical instruments is provided

• graduated ruler or scale

• compass

• protractor

• divider

• set-squares or set-triangles

ruler / scale

The geometrical instrument in the figure is called a "ruler".

A "ruler" is used to construct a straight line.

The marks or graduations on the ruler show the length measure in millimeter and centimeter.

Other than to construct straight lines, A "ruler" is used to measure a line-segment.

The word "ruler" means: a straight stick.

The word "ruler" is derived from a root word meaning straight stick.

The phrase "graduated ruler" means: a straight stick with grade of length measure marked on them.

Note: A ruler is also referred with the name "scale".

summary

Graduated Ruler or scale : A ruler is a straight stick with grade of length measure marked. It is used to construct straight lines and measure a line-segment.

compass

The geometrical instrument in the figure is called a "compass".

A "compass" is used to construct an arc of given radius. The arc has points that are in equal distance from the center point.

The word "compass" is (possibly) from root words "com+pace" meaning "together+take-steps".

summary

Compass : An instrument to measure a length and construct an arc of a given radius.

divider

The geometrical instrument in the figure is called a "divider".

A "divider" is used to measure the length between two points.

summary

Divider : is a geometrical instrument which is used to measure the length between two points.

protractor

The geometrical instrument in the figure is called a "protractor".

A "protractor" is used to mark an angle of given measure.

The word "Protractor" is from root words "protract+tor", which means "draw-out or lengthen a line".

summary

Protractor : is a geometrical instrument which is used to mark a measure of an angle.

set sequares

The geometrical instrument in the figure is called a "set squares" or a "set triangles".

The name "set squares" calls by the two $90^{\circ}$ $90^@$ angles provided by the instruments.

The name "set triangles" calls by the shape of the two pieces. Both names are used.

A "set squares" is used

• to construct perpendicular and parallel lines

• to measure standard angles $90^{\circ}$ $90^@$ , $30^{\circ}$ $30^@$ , $45^{\circ}$ $45^@$ , $60^{\circ}$ $60^@$ etc.

summary

Set Squares or Set Triangles : is a pair of triangular pieces used to construct parallel lines or to measure the standard angles $90^{\circ}$ $90^@$ , $30^{\circ}$ $30^@$ , $45^{\circ}$ $45^@$ , $60^{\circ}$ $60^@$ etc.

summary

Graduated Ruler or scale : A ruler is a straight stick with grade of length measure marked. It is used to construct straight lines and measure a line-segment.

Compass : An instrument to measure a length and construct an arc of a given radius.

Divider : is a geometrical instrument which is used to measure the length between two points.

Protractor : is a geometrical instrument which is used to mark a measure of an angle.

Set Squares or Set Triangles : is a pair of triangular pieces used to construct parallel lines or to measure the standard angles $90^{\circ}$ $90^@$ , $30^{\circ}$ $30^@$ , $45^{\circ}$ $45^@$ , $60^{\circ}$ $60^@$ etc.

Outline