# [Elementary 4] How to express the size of an angle and how to use a protractor

This time it's about "angles and their sizes" that we learn in XNUMXth grade math.

Content to explain!

1. What is the size of an angle
2. How to measure angles (How to use a protractor XNUMX)
3. How to draw angles (How to use a protractor XNUMX)

This is an explanation of angles that are the basis of various shapes such as quadrilaterals!

This site is created by Dr. Thomsontom labIt operates under the name

## angle and its size

the size of the anglehow far the line has turnedis determined by

The unit of the size of an angle is "degree (°)".

The first state is $$0°$$.If you go straight up from there, $$(90°)$$

It is $$180°$$ when it goes to a straight line, and $$360°$$ when it goes around.

A protractor can measure from $$0°$$ to $$180°$$!

## How to measure angles (How to use a protractor XNUMX)

Now let's see how to measure the size of an angle.

You need a protractor to measure angles!

XNUMX steps to measure the size of an angle
1. Align the center of the protractor with the vertex (①)
2. Align $$0°$$ line with side ①②
3. Read the memory above side ①③

In the angle shown in the figure, side ①③ is on $$75$$, so the size of this angle is $$75°$$.

## How to draw angles (How to use a protractor XNUMX)

I checked the angle you mentioned earlier several times.

Next is how to decide the angle and write the angle.

5 steps to draw corners
1. Draw line segment ①②
2. Align the center of the protractor with the vertex (①)
3. Align $$0°$$ line with side ①②
4. Hit the point ③ at the memory of the angle you want to write
5. Draw a line through points XNUMX and XNUMX

This time I wrote an angle of $$75°$$, but if you want to write an angle of $$120°$$, it is OK if you type point ③ in the memory of $$120$$.

Thomson

If you can draw the corners in the size you want, you can use it when drawing triangles and quadrilaterals!

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