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Protractor definition how to#

Now mark the point as B on the top circular part of a protractor, according to the preferred angle for example 40°.Now, place the protractor at that point, and its midpoint should touch the marked point O.

Protractor definition how to#

How to Construct an Angle (using protractor)

Wall clocks use the concept of angles to show time with hour and minute hands.

Artists use their measurement knowledge to sketch or create art pieces.

Carpenters use it to make equipment like doors, chairs, sofas, tables, etc.

Athletes use its concept in sports to enhance their performance.

Engineers construct buildings, bridges, houses, monuments, etc., using angle measurement.

Here, ∠AXD and ∠CXD are supplementary angles. Supplementary angles: Angles that add up to 180° (a straight angle) are called supplementary angles. Here, ∠BXC and ∠CXD are complementary angles. Complementary and Supplementary Angles:Ĭomplementary angles: Angles that add up to 90° (a right angle) are called complementary angles.

Here, ∠ABC, ∠BCA and ∠CAB are interior angles.Įxterior angles: Exterior angles are the angles formed outside a shape, between any side of a shape and an extended adjacent side. Interior angles: Interior Angles are the angles formed within or inside a shape. A reflex angle measures between 180°- 360°.An angle measuring exactly 180° is a straight angle.A right angle precisely measures 90° at the vertex.An obtuse angle is between 90° and 180°.An acute angle measures less than 90° at the vertex.In the given diagram below, OA is the terminal side.īased on their measurements, here are the different types of angles: Terminal Side: The side up to which the angle measurement is done.Initial Side: Also known as the reference line, a straight line from where an angle is drawn.Arms: The two sides of the angle, joined at a common endpoint.Vertex: A vertex is a corner of an angle, a point where two lines/sides meet.Angles are measured in degrees (°) using a protractor.įor example, 45 degrees is represented as 45° Parts of Angles

There are many daily life examples of an angle, such as cloth-hangers, arrowheads, scissors, partly opened doors, pyramids, edge of a table, edge of a ruler, etc. The word angle comes from a Latin word named ‘angulus,’ meaning “corner.” The common point of contact is called the vertex of an angle. If your angle has more than 180?, mark the 180? position and measure the additional degrees from there.An angle is formed when two straight lines or rays meet at a common endpoint. Where it crosses the curve of the protractor determines the number of degrees (?) of the angle. Check to see that the 0? is among the inner or outer sets of numbers, then note the position of the other side of the angle. This will tell you which set of numbers to read.To measure an angle, put the vertex of the angle at the hole or cross hairs, then turn the protractor so one side of the angle aligns with a zero point. When you line up the protractor along one side of an angle, it will be lined up at 0? (on either the inner or outer set of numbers). One set ascends from 0? to 180? (left to right) and the other set descends from 180? to 0? (right to left). Most protractors have two sets of numbers for each marking so you can measure an angle from either side. Along the curved part of the protractor there are number markings (also called calibrations), with 90? in the middle. Sometimes there are no numbers on this line, but 0? or 180? are measured from here. Usually a horizontal line goes through this point and from one side of the protractor to the other. This is where the vertex (point of the angle) must go when measuring. On the flat side of the protractor in the middle is either a hole or cross hairs. A semicircular tool for the measurement and construction of angles.