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SAT Math: Calculating a Circle's Radius When Given Its Center and a Point on Its Circumference 1 Views


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Description:

What is the radius of a circle with a center at (-4, 5) and a point on the circumference at (2, 13)?


Transcript

00:00

Yeah Whoa Okay A satay mash bumpers moron circles What's

00:06

the radius of a circle in the center and negative

00:07

for five and a point on this Or conference at

00:10

two Thirteen So there are two ways to tackle this

00:15

problem but usually we play two hand touch Teo keep

00:18

from hurting it because math problems don't wear protective headgear

00:22

Well here's a standard form circle where H K's a

00:24

center Yeah you know this one Well plug in the

00:26

centre point for H and K being careful about the

00:29

signs Yeah I saw the sign song about that So

00:32

we've got X plus four squared Plus Wyman five squared

00:36

equals R squared were only given a random point on

00:39

this circle And we can put that point to good

00:41

use So just plug it in for X and y

00:43

It's how easy this is We love circles so we

00:45

get two plus four squared plus theta two minus five

00:47

squared equals R squared Well six squared plus eight square

00:50

It is you thirty six plus sixty fourths Hundreds are

00:54

scared So are squared of one hundred which is in

00:56

the radius of the circle Just ten Yeah well that

00:59

was one way to solve the problem Another way would

01:01

be with a distance formula the distance from the centre

01:04

to any part of the circle's edge Is the radius

01:06

rights basically the definition Well we could have used the

01:09

distance formula to measure the distance from the center to

01:11

a random spot on the edge by plugging in the

01:13

values of the two points that were given like this

01:16

So the distance is ah this thing And then we

01:19

just plug in the negative four minus two squared plus

01:22

five minus thirteen square there And that gets us formula

01:26

Looks a whole lot like what we just did only

01:28

coming at it from a side view mirror Well either

01:30

way works but whichever you choose tackle it gently so 00:01:33.23 --> [endTime] it's Mom doesn't get too worried and that's it

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