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looking finding the perimeter of a rectangle
a rectangle paid this time we've given
been given a rectangle that has one side
with a measure of three
and a diagonal measure of 5
I'm gonna focus on half my rectangle
am gonna look at this triangle so let me draw that triangle
outside if the figures so we can see a little more clearly
I have a right angle right here
as we know we have a right angle at the corner of a rectangle
we have a height of three and this
diagonal of 5 but what we've created as a right triangle where we know the
hypotenuse
or C is 5 in one of the legs
a high right triangle is Trina got a call that
we used this formula called the pythagorean theorem
to figure out the missing side something right down a squared plus B squared
write a squared plus b squared equals csquared
A and B are my two legs
square 3 and solve for B
B is my unknown side in C
is my hypotenuse so fives squared that 9
so c squared is equal to 25
so b squared must be sixteen
nd miss equal to 4
this side up my right triangle is 4
now let's go back and label it in the rectangle
so that makes this side for now I can find my perimeter of the rectangle
because the opposite sides are equal
site is for the of this site is for
so if this side is 4 the opposite side is 4
and i no longer have to use the information on the diagonal
we don't need the diagonal just to find the perimeter so we used at five just to
find their missing side
so now as at our first four sides ap
and and the four sides at to get our perimeter of the rectangle
some plug in three plus for
plus three plus four
equals 7 plus 7 equals 14
teen and the units on this one
for ft he wishes feet says come back in
and are units and that's how you find
so that is how you find the perimeter given the diagonal
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