Name:
Circles Print Activity
Use the “Explore It” mode to answer the following questions.
1. Use the diagram below to answer the following questions:
a. A is a/an
angle.
(central/inscribed)
b. A is subtended by the red arc
c. A is inscribed in arc
.
.
(BA/AC/BAC)
2. Select
and then click
to answer the following:
a. A and B are subtended by the red arc
.
b. A is inscribed in arc
.
(DA/DAB/DABC)
c. B is inscribed in arc
.
(DB/ABC/DABC)
d. A  B  ______ .
e. D  C  ______ .
f. Drag A and B along arc DABC. Angles
size.
and
change in
g. Click
arc
and drag C along arc CD. C and D are subtended by the red
.
h. Click
change?
and change the size of the circle. Do any of the angle values
.
(Yes/No)
i. Click
change?
and change the location of the circle. Do any of the angle values
.
(Yes/No)
j. Conclusion: Angles subtended by the same arc are
.
(equal/unequal)
Junior High Math Interactives
2007 Alberta Education (www.LearnAlberta.ca)
Shape and Space/ Circles/ Object Interactive / Print Activity
Page 1 of 6
3. Select
Click and click
A  55 as shown in the diagram below.
. Drag D to the right until
a. B  ______ .
b. C  ______ .

c. D  ______ .
d. The angles subtended by arc AB are
 ______ and  ______ .
e. The angles subtended by arc DC are
 ______ and  ______ .
f. Conclusion: Angles subtended by the
same arc are __________.
4. Select
and click
to answer the following:
a. The inscribed angle is  ________ and it is subtended
by the red arc ________.
b. The central angle is  ______ .
c. A  ______  and COB  ______  .
d. Drag A around the circle until it measures 110.
COB  ______  .
e. Click
and drag C to the right to make central COB = 40. The inscribed
angle is now ______ .
f. Click
and drag C to the left to make inscribed A = 100. The central
angle is now _______ .
g. Click
and change the size of the circle. Do any of the angle values
change? __________.
(Yes/No)
h. Click
and change the location of the circle. Do any of the angle values
change? __________.
(Yes/No)
Junior High Math Interactives
2007 Alberta Education (www.LearnAlberta.ca)
Shape and Space/ Circles/ Object Interactive / Print Activity
Page 2 of 6
4.
con’d…
i. Conclusion: The central angle measures ___________ the inscribed angle
subtended by the same arc.
(half / twice)
5. Select
and click
. Move B to the left until the
central angle COB = 40 as shown in the diagram below.
a. The inscribed angle is  ______ .
b. The inscribed angle and the central angle are
subtended by the same arc _______.

c. COB = 40 and the inscribed
angle = _______ .
.
d. Change the size of the circle. Do any of the angle values change?
.
(Yes/No)
e. Change the location of the circle. Do any of the angle values change?_____.
(Yes/No)
f. Conclusion: The central angle measures ___________ the inscribed angle
subtended by the same arc.
(half / twice)
6. Select
and click
to answer the following:
a. The red tangents to the circle are _____
and _____.
b. The tangent lengths are _____________.
(equal/unequal)
c. C  D  ______ .
d. Move A around the outside of the circle.
C  D  ______ .
e. Move C and D around the circumference of the circle. C  D  ______ .
f. Move B around the circle. OB, OC and OD are _________ in length.
(equal/unequal)
Junior High Math Interactives
2007 Alberta Education (www.LearnAlberta.ca)
Shape and Space/ Circles/ Object Interactive / Print Activity
Page 3 of 6
6. cont’d…
g. Change the size of the circle. Do the tangent lengths change? _______
(Yes/No)
Do the sizes of C or D change? ________
(Yes/No)
h. Change the location of the circle. Do the tangent lengths change? _______
(Yes/No)
Do the sizes of C or D change? ________
(Yes/No)
h. Conclusion: A tangent to a circle is perpendicular to the ___________ at the point
of tangency.
(chord/radius)
7. Select
and click
to answer the following:
a. CD is called a ____________.
(chord/radius)
b. The midpoint of CD is_______.
(A/0/B)
c. The radius shown is ________.
d. Move B around the circle until it intersects the chord CD at 90. When the radius
passes through the midpoint of the chord, the lengths of CA and DA (or CE and
DE) are _________.
(equal/unequal)
e. Click
and move midpoint A until the chord CD intersects OB at 90. The
lengths of CA and DA (or CE and DE) are ______________.
(equal/unequal)
f. Click
and move C and D around the circle until the chord intersects line
OB at 90. The lengths of CA and DA (or CE and DE) are __________.
(equal/unequal)
g. Using the diagram from part f above, change the size of the circle. The lengths
of CA and DA (or CE and DE) are __________.
(equal/unequal)
h. Using the diagram from part f above, change the location of the circle. The
lengths of CA and DA (or CE and DE) are __________.
(equal/unequal)
Junior High Math Interactives
2007 Alberta Education (www.LearnAlberta.ca)
Shape and Space/ Circles/ Object Interactive / Print Activity
Page 4 of 6
7. cont’d…
i. Conclusion: The perpendicular from the centre of a circle bisects the __________.
(chord/radius)
8. Select
and obtain the diagram below to answer the following:
a. OB is a ___________ of the circle.
(chord/radius)
b. CD is a ___________ of the circle.
(chord/radius)
c. OB intersects CD at and angle of _____ .
d. The perpendicular from the centre of a circle
bisects the _____________.
(chord/radius)
e. If CD measures 10 cm then CA and DA measure _______ cm.
9. Select
and click
. Drag CD around the circle until A is on
centre O and CD measures 16 as shown below.
a. The length of AC = ________.
b. The length of radius OB = ________.
c. If the chord passes through the centre of
circle and is twice the length of the radius,
then the chord CD must be the
.
(diameter/radius)
Junior High Math Interactives
2007 Alberta Education (www.LearnAlberta.ca)
Shape and Space/ Circles/ Object Interactive / Print Activity
Page 5 of 6
10. Each diagram below is an example of one of the circle properties. Match the
Circle Property to the diagram it illustrates.
Circle Properties:
Chord: The perpendicular from the centre of a circle to a chord bisects the chord.
Central Angle:
The measure of the central angle is equal to twice the
measure of the inscribed angle subtended by the same arc.
Inscribed Angle: The inscribed angles subtended by the same arc are equal in
measure.
Tangent: A tangent to a circle is perpendicular to the radius at the point of tangency.
Property:________________
Property:__________________
Property:______________
Property:_______________
Junior High Math Interactives
2007 Alberta Education (www.LearnAlberta.ca)
Shape and Space/ Circles/ Object Interactive / Print Activity
Page 6 of 6