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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
Full Transcript
- 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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