10-1 Circles and Circumference

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# 10-1 Circles and Circumference - PowerPoint PPT Presentation

10-1 Circles and Circumference. Circle. The locus of all points in a plane equidistant from a given point called the center . Circles are named by their center point Chord - any segment with endpoints on the circle Diameter - The chord passing through the center of the circle

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## PowerPoint Slideshow about '10-1 Circles and Circumference' - derek-mccormick

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### 10-1 Circles and Circumference

Circle
• The locus of all points in a plane equidistant from a given point called the center.
• Circles are named by their center point
• Chord- any segment with endpoints on the circle
• Diameter- The chord passing through the center of the circle
• Radius- a segment whose endpoints are the center of the circle and a point on the circle
Example:
• Circle R has diameters ST and QM
• If ST=18, find RS
• If RM=24, find QM
• If RN=2, find RP

Q

P

S

R

T

N

M

Examples:
• Diameter of x = 22, diameter of Y =16 and diameter of Z =10
• Find EZ and XF

X

Y

Z

E

G

F

Circumference
• The distance around the circle
• C = πd or C = 2πr

(where π≈3.14, d is diameter and r is radius)

Example: Find circumference if r = 13 inches

Example:
• Find the EXACT circumference

### 10-8 Equations of Circles

Standard equation
• For a circle with center (h, k) and radius r

x and y are variables and must ALWAYS be in your answer!

Example: Write the equation of the circle
• With center (-1, 3) and radius
• With endpoints of the diameter (4, 6) and (-2, 6)
To graph a circle:
• Find the center (h, k)

(remember that the formula is x-h and y-k so when naming the center you do the opposite of the equation)

Find the radius by taking the square root of the number after the =

Plot the center and count out for the radius