Question

OpenStudy (anonymous):
Lines CD and DE are tangent to circle A as shown below:

Lines CD and DE are tangent to circle A and intersect at point D. Arc CE measures 130 degrees. Point B lies on circle A.

If arc CE is 130°, what is the measure of ∠CDE?

20°
40°
42.5°
50°

Answer 1

do you can post an image about this ?

Answer 2

yea

Answer 3

do you know how many degrees has a circle ?

Answer 4

180 I think or 360

Answer 5

or it has none?

Answer 6

the degree in thepicture i sent says 130

Answer 7

a circle has 360 degrees

Answer 8

yea

Answer 9

you know arc CE equal 130 degrees
can you calcule arc CBE howmany degrees has ?

Answer 10

i don't know how unfortunately

Answer 11

I think they are all the same because of the distance between each other

Answer 12

so 130 degrees

Answer 13

?

Answer 14

remember a circle has 360 degrees
arc CE has 130 degrees

how you get the measure of arc CBE ?

Answer 15

divide 360 by 130

Answer 16

not really

Answer 17

use a+b = 360
a=130

how you calcule the value of b ?

Answer 18

i got 230

Answer 19

thats b

Answer 20

230 right?

Answer 21

yes ofc so you get arc CBE has 230 degrees

Answer 22

yea

Answer 23

now what next

Answer 24

do you know this formula ?

exterior angle measure = (big arc measure - small arc measure)/2

Answer 25

or look please on this website

https://www.mathwarehouse.com/geometry/circle/tangents-secants-arcs-angles.php

Answer 26

You can use a simple rule:
The angle between two tangents is supplementary with minor arc.

Answer 27

It means mCE + mCDE = 180

Answer 28

@extrinix