welcome to math with mr. J in this video I'm going to cover complementary and supplementary angles I'm going to talk about what those words mean and then we're also going to take a look at how to find missing complementary angles and missing supplementary angles we have two complementary examples and two supplementary examples so let's jump right in to number one for number one we have complementary angles complementary angles are angles that add up to equal exactly 90 degrees so for number one we're given a 70 degree angle we need to figure out what this x equals to equal 90 degrees so 70 plus what equals 90 degrees and some of these are harder than others so some you may be able to figure out using mental math some you may not so what we can do we take the 90 degrees that we want to get to and subtract what we're given we're given that 70 degrees that's that's our known subtract these and that difference is what X is going to equal so 90 degrees minus 70 degrees equals 20 degrees so x equals 20 degrees and let's double check 70 degrees what we were given Plus that 20 degrees gives us 90 degrees again complementary angles add add up to equal exactly 90 degrees number two these are complementary angles as well we haven't known here we're given 48 degrees so we need to find what y equals so we can take our 90 degrees that we want to get to subtract what we're given and that difference will be what y equals so 90 minus 48 degrees gives us 42 so y equals 42 degrees 42 plus this 48 equals 90 degrees so 48 degree angle and a 42 degree angle our complimentary number three and number four we're going to move to supplementary angles supplementary angles have to equal 180 degrees so for number three we have a 65 degree angle we need to find what angle a equals an order to get to 180 degrees so we use the same strategy we can use our 180 subtract our given or known 65 degrees 180 minus 65 equals 115 degrees so a equals 115 degrees so let's double check that 115 degrees plus the known of 65 degrees equals exactly 180 degrees so that 115 and 65 degree angle are supplementary so let's move on to number 4 where we are given 128 degrees and we need to find what angles Z equals these are supplementary angles so we know they have to equal 180 degrees let's subtract what we're given 128 degrees and that gives us 52 degrees so Z equals 52 degrees and 52 plus 128 degrees equals exactly 180 so they are supplementary now one thing I do want to mention before we end here this is how I remember which is which as far as complementary and supplementary the see here is a lower letter in the alphabet so it aligns with the our number s is further along in the alphabet than C so it aligns with the higher number so there you have it there's complementary and supplementary angles I hope that helped thanks so much for watching until next time peace