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10.06 Tangents to a circle

Interactive practice questions

In this question we aim to prove that the tangent is perpendicular to the radius drawn from its point of contact.

In the diagram, $C$C is an arbitrary point on the line $AD$AD, and $B$B is the point at which the tangent meets the circle.

a

What can we say about the lines $OB$OB and $OC$OC?

$OB=OC$OB=OC

A

$OB>OC$OB>OC

B

$OBOB<OC

C
b

What point on $AD$AD is closest to the center of the circle?

Point $A$A

A

Point $B$B

B

Point $C$C

C

Point $D$D

D
c

In general, what can we say about the angle of a line joining some point to some other line by the shortest route?

The angle is obtuse.

A

The angle is reflex.

B

The angle is a right angle.

C

The angle is acute.

D
d

Hence, what can we say about angle $\angle OBA$OBA?

Straight angle

A

Acute angle

B

Reflex angle

C

Right angle

D
Easy
1min

In the figure below, $AC$AC is tangent to both circles.

Easy
2min

In the diagram, $AC$AC is a tangent to the circle with center $O$O. What is the measure of $x$x?

Easy
< 1min

If $\overline{BA}$BA is a tangent to the circle, determine the value of $x$x showing all steps of working.

Easy
1min
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Outcomes

G.C.2

Identify and describe relationships among angles, radii, chords, tangents, and arcs and use them to solve problems. Include the relationship between central, inscribed, and circumscribed angles and their intercepted arcs; inscribed angles on a diameter are right angles; the radius of a circle is perpendicular to the tangent where the radius intersects the circle.

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