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ACT Aspire Math: Calculating the Radius of a Circle Using A Right Triangle 0 Views


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Description:

In the diagram shown, C is the center of the circle, D is the midpoint of AB, and AB = 2, while CD = 10.


Transcript

00:03

Okay More shmoop math for you Here we go Circle

00:06

time in the diagram shown sees center of the circle

00:09

These the mid point a b and a b is

00:11

too While cd that thing is ten Well what is

00:15

the radius of the circle Time to get rad radius

00:22

Whatever We'll be here all night folks The radius of

00:24

the circle is the hypothesis of the right triangle cdb

00:28

or the congruent right triangle a cd we confined cb

00:32

using the pythagorean theorem right c b squared equals c

00:36

d squared plus d b squared The problem tells us

00:40

that two cd is ten so c d then is

00:44

ten over two or five Right So since d is

00:46

the midpoint of a b we also know that d

00:49

b is five right It's the same well plug these

00:52

values in the formula above and that gets us we'll

00:55

see b squared is five squared plus five sward or

00:57

twenty five plus twenty five or fifty Then we just

01:00

take square root of each side and simplify it using

01:03

the fact that while fifty is twenty five times too

01:05

Right so we got square to fifty Factor out that

01:07

twenty five times two We get square root of twenty

01:10

five which is five times for it to so that's

01:13

it The radius of a circle is five times Where

01:15

were you two units The answer is d and we

01:18

are done

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