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In this chapter, we will study the definition and vocabulary as well as the different types of angles (acute, obtuse, complementary, supplementary, right null, flat, reentrant and salient. Later, we will review the use of the protractor and the bisector of an angle.
Students will be expected to construct and trace angles and measure with a protractor. The mastery of the different angles and definitions of the course must be mastered since these notions will be recurrent in the sixth grade and throughout your schooling.
I. Notion of angles
An angle is a portion of the plane bounded by two half-lines having the same origin.
1. vocabulary
- The point O is the vertex of the angle.
- The half-lines [ox) and [Oy) are the sides of the angle.
2. scoring
- The portion of the plane colored in blue is a salient angle.
- The uncolored portion of the plane is a re-entrant angle.
Example:
What is the name of the blue angle?
It can be named in different ways (most often with three letters, the middle one
is always the vertex of the angle):
3. angles of the same measure
Two angles of the same measure are coded by the same symbol (as for lengths).
Example:
In the figure below, what are the angles of the same measure?
These angles are coded with the same symbol, so we have .
II. the different types of angles
The angles are classified by category according to their measure.
III. Use of the protractor
You can measure an angle or draw an angle of a given size with a protractor. The unit is the degree.
Did you get that lesson on angles in 6th grade?
Un QCM de maths sur les angles en 6ème.
Skills to assimilate on the angles:
- Know the definition of an acute, obtuse, right and flat angle;
- Know how to draw an angle using a protractor;
- To know how to measure with a protractor and to calculate, also, its measure on a geometrical figure;
- Complementary and supplementary angles;
This course is in accordance with the official programs of thenational education.
In addition, you can continue with the exercises on the bisector of an angle in the sixth grade.
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