1TH/Vwo §4.4 Measuring angles

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§4.4 Measuring angles ...

is on the menu today!

1TH/Vwo §4.4 Measuring angles

First a quick check on your knowledge of §5.3 !

Try to give the good answers, gaining points.

an angle of 90 degrees is a(n) ...

1. straight angle
2. obtuse angle
3. right angle
4. acute angle

An angle of 47 degrees is a(n)
...... angle.

1. obtuse
2. right
3. acute
4. straight

An obtuse angle could be ...

1. 99 degrees
2. 36 degrees
3. 90 degrees
4. 180 degrees

an angle of 103 degrees is a(n)
angle

1. acute
2. right
3. obtuse
4. straight

I wonder if    .....

+ you had all questions right, knowing all about it, or

+ you had both wrong, having no clue

However, let's look back at the Theory from §4.3 !

Attention (1):

+ a right angle has :

+ an acute angle has a number of degrees between  0  and  90.

90°

Attenzione (2):

+ an obtuse angles has a number of degrees between 90 and 180

+ a straight angle has 180 degrees

Ready for §4.4 Measuring angles?

Soon comes a Movie.

Measuring angles ...

+ you can do with the GEO TRIANGLE:

  using the PROTRACTOR ( =gradenboog) on it

+ that's the semi-circle (=half a circle) with the degrees from 0 - 180 degrees

    written on it

+ just watch the following Movie and be amazed!

Ruben ...

surely knows how to explain things in a simple way!

By the way, I offer you this Dutch movie, because it was the only one I found that used a Geo triangle and not a compass rose!

Now...

Your teacher will demonstrate how to MEASURE angles

with a GEO triangle.

After this Ruben will take over!

(But who the heck is Ruben?!)

How many degrees is angle P?

First notice this: 

 + the 0-point of the GEO lies on the vertex of the angle

 + the longest side of the GEO lies along one of the arms of the angle

  

How many degrees is angle P?

There are two possible answers:

We read off 64 degrees and also 116 degrees.

Is this angle acute or obtuse? It's acute because it lies between

0 and 90 degrees.

So 64 degrees is the good answer!

Homework time

Make the tasks.

Correct them with the Solutionsbook.

Later a few more slides follow.

Good luck!

 3 special things:

+ A difficult word for your wordlist

+  Which angle is meant?

+ How to measure an angle if the arms are too short?

  Just watch the next slides!

Please add to the Wordlist:

an AUXILIARY line - een hulplijn

in opposite directions - in tegengestelde richtingen

a pentagon - een vijfhoek

a hexagon - een zeshoek

If the arms of an angle are too short, just ....

extend them!

So in this case

you take your pencil and 

make both arms longer,

so that the geo can be used well! 

(You may even do this in your Textbook, 

but with a PENCIL, of course!)

In the picture you see many different angles:

+ angles A, C and E , but also

+ angles B1, B2, D1 and D2 !

+ so by the added number you

   know which part of the angle 

   is meant. Great!

Time for Homework

+ Do:    § 4.4 Measuring angles

+ Check your work with the Solutionsbook

+ take pics and

+ send in all the stuff on Google Classroom