in this video I'm going to show you how to measure angles using a protractor so hello everyone and welcome to mathematics with Marlene when we have a line we can easily measure this line using a ruler for instance this line is six centimeter long but what if we have two rays and we want to measure the angle between these two rays now we can't use a ruler anymore we need to use a protractor to measure this angle and this angle is a hundred and ten degrees and degrees is the unit in which we measure angles so always remember the degrees but how do I measure angles let me show you here we have two rays and we want to measure this angle between the two rays so first we need our protractor and then there are two things I want you to remember before you measure your angle the first thing can you see in the middle at the bottom of your protractor there is that t this might look different on different protractors sometimes there's a DOT other times there's just this T and other times there's a little hole to indicate with this space but all I wanted to remember is to line up the bottom middle part of this projector with the vertex of the angle and the second thing I want you to remember is to line up this bottom horizontal line of the projector with one of the Rays so let's follow those two steps before we measure the angle so first we line up the middle bottom part of the protractor with the vertex and then we make sure that the bottom line of the projector lines up with one of the Rays I chose the Purple Rain and now we can measure the angle but before we do that are we going to use the outer numbers to measure the angle or are we going to use the inner numbers to measure the angle you always want to start at zero so in this case because our purple Ray is pointing at zero here we are going to use the inner numbers and now we can measure the angle so our purple Ray is at zero and our green ray is at 80 degrees so this angle is exactly 80 degrees and always make sure to remember your degrees it's not just 80 it's 80 degrees but how about this angle we want to measure this angle between these two rays first we line up the bottom middle part of the protractor with the vertex of the angle and then we make sure we line up the bottom part of the protractor with one of the Rays and now we can measure the angle but now do we use the outer numbers or do we use the inner numbers again remember we want to start at zero and our purple array points to the zero on the outer numbers so we are going to use the outer numbers and now we can measure the angle so our purple Ray is at zero degrees and our green ray is at 115 degrees but if you can't see clearly that your ray is pointing at 115 degrees make sure you extend that Ray so that you can see exactly to where the ray is pointing and it is pointing at exactly 115 degrees but sometimes we can have another problem our protractor only measures from 0 to 180 degrees but what if we have an angle that's bigger than 180 degrees how will we measure this angle we can still very easily measure this angle the first thing we're going to do is we're going to measure 180 degrees and then we're going to measure the rest of the angle and add these two together to get the whole angle so let's do that step by step first we're going to measure 180 degrees so we line up the middle bottom part of the protractor with the vertex and then our purple red is pointing at zero on the right so we use the inner numbers and we measure exactly 180 degrees so the first part is 180 degrees and now we can add the rest of the angle I'm going to keep the middle bottom part of my protractor on the vertex but I'm going to tilt the protractor and now I'm going to use the outer numbers because this green ray is pointing at the zero on the outer numbers I'm going to use the outer numbers to determine how many degrees the rest of the angle is and the rest of the angle is 30 degrees and now I just add these two together to get 210 degrees the whole angle is 213 degrees and just like in all my other videos there will be a free worksheet and memo in the description box below make sure you click on the link to go and download the free worksheets and memo and if you haven't already and this video helped you please remember to like this video and to subscribe to my channel and then I'll see you in the next video goodbye [Music]