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# circles - PowerPoint PPT Presentation

circles. 10.1 Tangents to Circles. Circle Radius Diameter Chord Secant Tangent. Write the following down. Tangent. Circle. Radius. Diameter. Chord. Secant. Based on the picture write your own definitions….

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## PowerPoint Slideshow about ' circles' - milica

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Presentation Transcript

### circles

10.1 Tangents to Circles

Circle

• Diameter
• Chord
• Secant
• Tangent
Write the following down

Talk to the person NEXT TO YOU about what you got for each of your definitions.

Circle –

a set of all points in a plane that are equidistant from a given point

distance from the center to a point on a circle.

Diameter –

the distance across a circle through the center.

Chord –

• a segment whose endpoints are on the circle.
• Is the diameter a chord?
• Yes, but it passes through the center of the circle.

Secant –

• a line that intersects a circle in two points.
• Tangent –
• a line that intersects a circle at exactly one point.

Draw two congruent circles.

• What property do they share?
• Circles are congruent if they have the same radius.

2

2

Congruent?

c

CD

d

k

Common Internal Tangent – Intersects the segment that joins the centers of the two circles.

D

C

j

m

Common External Tangent – Does not intersect the segment that joins the centers of the two circles.

A

B

Common Tangents

n

144 + 256 = 400

• It’s a right triangle!
• So the segment is

perpendicular.

So the segment is tangent.

16

12

20

Pythagorean thm.

144 + 100 = 240.25

• not a right triangle
• So it’s not perpendicular.

10

12

15.5

Pythagorean thm.

B

16 ft

r

C

A

r

8 ft

Find the radius, given that BC is tangent to the circle, and therefore perpendicular to the radius.

A

C

B

Draw! (If two segments from the same exterior point are tangent to a circle, then they are congruent.

CA = CB

2x + 10 = 4x-15

• 25 = 2x
• 12.5 = x

2x + 10

4x - 15

Find x

### Homework

Pg. 599: 18-28, 36-41, 46-48