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## 4th grade

### Unit 11: Lesson 2

Angle introduction# Recognizing angles

Sal identifies acute, obtuse, and right angles in diagrams and pictures. Created by Sal Khan.

## Want to join the conversation?

- What are real world uses for being able to identify angles of objects?(2 votes)
- anything that's up and right perfectly is a right angle... if you crack an door open a little its a acute angle if you open a cabinet almost al the way its obtuse(3 votes)

- So obtuse angles will always be bigger than right angles?(2 votes)
- A right angle is exactly 90 degrees. An obtuse angle, on the other hand, measures more than 90 degrees but less than 180 degrees. So, an obtuse angle is always bigger.(6 votes)

- This teaches us about important stuff we need to know about angles at 90 or higher. 🌱🌿 But one thing: How can you tell a obtuse angle from a acute angle?(0 votes)
- An obtuse is bigger than 90 degrees and an acute is smaller than 90 degrees, It is easy to tell if it is acute angle if you think of the word CUTE. The angle is small and with small number so you would think of it it as cute. :)(1 vote)

- How do you get rid of your parole officer?(4 votes)
- What is the difference between an acute angle and a obtuse angle?

Also how can I tell if the angle is a acute angle,obtuse angle ,and a right angle?(3 votes)- An acute angle is less than 90 degrees. An obtuse angle is greater than 90 degrees but less than 180. You can tell by just looking to see if it's more or greater than 90 or exactly 90 and it goes from there!(2 votes)

- I wanted to know how can we know when there is a fraction of a angle(2 votes)
- It depends on how the angle is presented to you. Is it in a Triangle? If so, what other angles are given? What other information is given or not given? It all depends on the situation.(4 votes)

- the life need a seed and they need water and they need to be in the sun(3 votes)
- Um... are you going to finish dat cwosson?(3 votes)
- Who invented angles and why are angles important, Thank you to everyone for answering my question.🙂😊(2 votes)
- The second one is because it helps in construction jobs, and depending on how good you are with angles you can do many more things.(2 votes)

- I love angles thank you for this video!(2 votes)

## Video transcript

Look at the diagram below, then
answer the following question. What type of angle is the angle
highlighted in the green below? So it looks like
two anteaters going after an ant right over here. And this anteater is
going straight down, or at least on my
screen it looks like it's going straight down. And this anteater's going
straight to the left. And so it looks like this
one's going straight down, this one's going
straight to left. It looks like this is a right
angle or a 90-degree angle. And so if I have to pick
between any of these, it looks most like
a right angle. It looks like this is
exactly going down, and this is going
exactly to the left, that this is a
90-degree angle here. If this was an acute angle,
then the angle between them would be smaller. So maybe this top
one would be coming in from this direction
right over here. If it was obtuse, this
angle would be larger. So let's just check
our answer and try to do a few more of these. Which of the angles labeled
in the diagram below are acute angles? So just as a reminder, an acute
angle is less than 90 degrees. So let's see, A and C both
look larger than 90 degrees. But B and D both look
less than 90 degrees. So I'll go with B and D
are the acute angles here. Let's do another one of these. What type of angle is the angle
highlighted in green below? Well, this angle is
less than 90 degrees. If it was equal to 90
degrees, this thing would come out like this. So this is clearly
less than 90 degrees. This is an acute angle. Let me just do one more. This is a lot of fun. Select a symbol from
the drop-down menu to complete the
following statement. Then answer the question below. Angle A is less than 90 degrees. What type of angle is angle A? So angle A, it's
less than 90 degrees. So an angle less than 90
degrees is an acute angle. If it was exactly 90 degrees,
it would be a right angle. If it was larger
than 90 degrees, it would be an obtuse angle. So I will go with acute angle. And we got it right.