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### Course: 4th grade>Unit 12

Lesson 3: Decomposing angles

# Decomposing angles

Lindsay finds the measures of angles using addition.

## Want to join the conversation?

• What does decomposing mean?
(12 votes)
• Decomposing means breaking things into smaller parts to understand it better.
(31 votes)
• what does decomposing mean?
(0 votes)
• Hey kimchhay te

composing means putting together and the prefix de means not so decomposing means taking something apart

hope this helped!
(21 votes)
• how do you correctly do the angles? Like it could be mistaken for CAE or something like that. Does it matter?
(6 votes)
• Yes, it does as you go in order to find the angles when solving. It is possible either way but it is easier in order.
(3 votes)
• There is a point where the video dosent explain the work, for example it says what is the measurement of y. Hint z is a straight angle it dosent explain how in the videos to solve that
(3 votes)
• how did she add the angles?
is it like normal addition?
(4 votes)
• it is kind of like addition and subtraction except you have to do one step and there is degrees.
(3 votes)
• help! I do not understand
(4 votes)
• Hi Imorris!
How can I help you?
This video is a little tricky, but let's work through it step by step.
Let's find angle EAC.
Decomposing means breaking things down.
So to find angle EAC, we would usually need a protractor (which is a handy angle-finding tool) but if you do not have one, there is an easy way to do this. Angle EAD = 60 degrees. Angle DAC = 75 degrees. Angle EAC is the combine measurement of these two angles. What is 60 degrees plus 75 degrees? 135 degrees. 135 is the combined measurement of the two smaller angles making up EAC. This is how we can solve for EAC.
I hope this helps!
(1 vote)
• Can there be a negative angle? Like if you were to bend yourself 45 degrees backwards?
(1 vote)
• A angle can never be negative, since it is a measurement. The lowest a angle can be is 0.000000...1, and anything lower would be no angle, or at least to the naked eye. The largest an angle can be is 360 degrees, which is a full circle. So to bend 45 degrees "backward" you would either go 45 degrees in either the left or right direction, or you would go 315 degrees in the opposite way. It is all about the direction you decide your angle is going to extend to and from.
(5 votes)
• what does protracter mean and angle
(3 votes)
• is there more videos to make this understand more?
(3 votes)
• i think so
(1 vote)
• i don't get the video really well
(3 votes)

## Video transcript

- [Voiceover] What is the measure of angle EAC? So we have this symbol here, which means angle, and then these three letters, EAC. Now to measure angle EAC, we need to first find angle EAC down here on our picture, and the way we can do that is use these three letters and we're gonna go in the order that they're given to us. So the first letter we're told is E, so the first letter we'll find down here is E. From there, we'll go to the second letter, A. And then finally, we go to our last letter, C. Again, in the order that they were told to us. So this opening right here is our angle. We wanna know how many degrees is this opening? The most common way to measure an angle would be to use a protractor, but we're not given a protractor, so we can't do that, but we do have enough information on this diagram down here to solve this. What we can see is that our large angle EAC is made up of two smaller angles. This first one, angle EAD. Right here, angle EAD... plus from there, it picks up with angle DAC. Angle DAC. These two angles, this first one from here to here, and then the second from here to here, when they're combined, they make the same size opening as our angle. So if we can combine these two angles, we will know the measure of our angle because again, these two combined are equal to our entire angle. So let's do that, starting with EAD, we can see we're told, it's 60 degrees. That's a 60 degree opening. Plus angle DAC has a 75 degree opening, and so if we combine that, if we go 60 degrees to here plus another 75 down to here, we've covered our entire angle. Our entire opening in 60 plus another 75. So we can add these to solve for the measure of our angle. Six tens plus seven tens is 13 tens or 130. 13 and then that zero is there because we're talking about tens. Plus zero ones and five ones is five ones. And so 130 plus five is 135 degrees. So the measure of our entire angle, angle EAC is 135 degrees.