What does Alpha-Gamma-Delta mean

What is an angle

This is easy to explain using a flashlight as an example.

The beam of the flashlight is an overturned V. Inside the V there is light, outside it is dark.

The mathematician calls the "shape" of the flashlight one angle.

Designations on the angle

The flashlight beam is limited on the sides. This is also the case with the angle.
These side lines are called at angles leg. The point at which these two legs meet is called Vertex.

To distinguish between different angles, they are denoted with Greek letters: for example alpha $$ alpha $$. This means the entire yellow area.

Sometimes you will see that angles are given by means of sequences of points.

Angle $$ alpha $$ $$ = $$ angle BAC (angle from B via A to C)
short: $$ angle $$ $$ alpha $$ $$ = $$ $$ angle $$$$ BAC $$

The main Greek letters:
$$ alpha $$ = alpha
$$ beta $$ = beta
$$ gamma $$ = gamma
$$ delta $$ = delta
$$ epsilon $$ = epsilon

Types of angles

Angles can be of different sizes. You can imagine this using the example of the clock. The two pointers are the legs of the angle.

At 1:00 a.m .: hands form small angles

At 4:00 am: the angle is already much larger

At 9:00 a.m .: the angle is even bigger

And at 12:00 a.m. or 12:00 a.m.?
There are 2 options:


The first picture shows you the largest possible angle on the watch. The second picture makes it clear to you that a so-called Zero angle exists.

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How do you measure angles

You need a new one to measure angles unit and a new one Measuring tool.

  • The unit in which angles are measured is this Degree and gets the mark ° .

  • As a measuring tool you take a triangle ruler, because a "protractor" is drawn on it (yellow area).

A special angle

You often come across the in your environment right angle: Table edges, cupboards, magazine pages ... The right angle is 90 °.
On the clock it looks like this:

You can display all angles between 0 ° and 360 ° on the clock.

Types of angles

There are 3 special angle names:

$$ 1. $$ full angle = 360 °

$$ 2. $$ straight angle = 180 °

$$ 3. $$ right angle = 90 °

An exact number of degrees is assigned to these 3 types of angle. On the next page you will find the names for all other angle sizes.

Angles are marked with a small rotating arrow so that it is clear which area is meant:


The arrowhead is also often left out, so that only the arc remains.

Other types of angles

$$ 4. $$ Acute angle = more than 0 ° and less than 90 °

$$ 5. $$ obtuse angle = more than 90 ° and less than 180 °

$$ 6. $$ obtuse angles = more than 180 ° and less than 360 °

Here you can also set the angle yourself:

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