Some of the examples of supplementary angles include: ∠ ABD is a supplement of ∠ DBC because Supplementary angles are pair angles whose sum of degree measurements equals 180° (straight line). ∠ ABD is a compliment of ∠ DBC because ∠ ABD + ∠ DBC =90° (right angle). Two angles are said to be complementary to each other if their sum equals 90° (right angle). Alternate interior angles and alternate exterior angles.Angles PairsĪngle pairs are angles that appear in twos to display a certain geometrical property. You can use the same procedure to draw any angle less than 180°. Label your diagram such that A and C are the sides and B is the vertex of the angle.Using a ruler, join the dot with the mark on the line.Move anticlockwise along the protractor scale and place a dot at 50°.Place the base of the protractor on the line such that its center coincides with the mark.Draw a straight line of any dimension and place a dot along the line.Now, remove the protractor and then use a ruler to join the dot with the vertex mark.Find the given angle on the protractor scale and mark a small dot at the protractor’s edge.Place the middle of the protractor at the vertex dot and ensure the mark on the line and the protractor flashes center.The dot will represent the vertex of the angle. Mark a dot at any position on the line.The straight line will act as the arm of the angle. Draw a straight line of any measurement.Line up one line along the 0° mark on the protractor and follow the second line to read the angle.Īngles less than 180° can be drawn using a protractor by following the steps below: ![]() To measure angle “α = 30 o” between two lines, proceed as follows: Make sure the vertex of lines coincides with the midpoint of the protractor.įinally, follow the second line to read to the nearest degree the size of the angle. To measure an angle using a protractor, line up one line or ray along the protractor’s zero-degree line. You can read angles from a protractor either by moving clockwise or anticlockwise. A protractor is a transparent glass or plastic tool with calibrations in either in radian or degree scale. The modern way of measuring an angle is by the use of a protractor. You can see the best evidence of this method in the Egyptian Museum found in Berlin.Ī shadow was cast over a graduated stone tablet using a vertical rod known as “ Gnomon.” With this method, Egyptians were able to measure time and seasons accurately. The concept of measurement of angles is dated back to 1500 BC in Egypt, where it took the Sun’s shadows against graduations marked on stone tablets. ![]() ![]() Here, points A and C are the sides of the angle, while B is the vertex of the lines. ![]() Angles are represented using the symbol ∠ and the Greek letters such as θ, α, etc.įor example, ∠ ABC = θ. The units for measuring angles are the degree (°) and radian (rad). The rays or lines that join or intersect at a common point to form an angle are referred to as sides of the angle. In mathematics, an angle is defined as a geometric figure created by two rays sharing a common end point. For many such reasons, it is, therefore, necessary to study angles. And that’s how the clocks are designed to synchronize with the rotation of the Earth. It takes the earth 24 hours to rotate at an angle of 360°. For example, the minute hand of a wall clock turns angle 360 degrees to make a minute. Complementary and supplementary angles worksheet free.Angles – Explanation & Examples What is Angle?Īngles are useful in our daily life, so it’s important to learn and understand them.
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