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Example Questions
Example Question #31 : Circles
Refer to the above diagram. Evaluate the measure of .
The total measure of the arcs that comprise a circle is , so from the above diagram,
Substituting the appropriate expression for each arc measure:
Therefore,
and
The measure of the angle formed by the tangent segments and
, which is
, is half the difference of the measures of the arcs they intercept, so
Substituting:
Example Question #21 : Sectors
Figure NOT drawn to scale.
The above figure shows a quadrilateral inscribed in a circle. Evaluate .
The question cannot be answered from the information given.
If a quadrilateral is inscribed in a circle, then each pair of its opposite angles are supplementary - that is, their degree measures total .
and
are two such angles, so
Setting and
, and solving for
:
,
the correct response.
Example Question #31 : Circles
Figure NOT drawn to scale.
The above figure shows a quadrilateral inscribed in a circle. Evaluate .
The question cannot be answered from the information given.
The question cannot be answered from the information given.
If a quadrilateral is inscribed in a circle, then each pair of its opposite angles are supplementary - that is, their degree measures total .
and
are two such angles, so
Setting and
, and solving for
:
,
The statement turns out to be true regardless of the value of . Therefore, without further information, the value of
cannot be determined.
Example Question #11 : How To Find The Angle Of A Sector
Figure NOT drawn to scale.
The above figure shows a quadrilateral inscribed in a circle. Evaluate .
If a quadrilateral is inscribed in a circle, then each pair of its opposite angles are supplementary - that is, their degree measures total .
and
are two such angles, so
Setting and
, and solving for
:
,
the correct response.
Example Question #11 : How To Find The Angle Of A Sector
Figure NOT drawn to scale.
Refer to the above diagram. is a diameter. Evaluate
is a diameter, so
is a semicircle - therefore,
. By the Arc Addition Principle,
If we let , then
,
and
If a secant and a tangent are drawn from a point to a circle, the measure of the angle they form is half the difference of the measures of the intercepted arcs. Since and
are such segments intercepting
and
, it holds that
Setting ,
, and
:
The inscribed angle that intercepts this arc, , has half this measure:
.
This is the correct response.
Example Question #12 : How To Find The Angle Of A Sector
Figure NOT drawn to scale.
In the above figure, is a diameter. Also, the ratio of the length of
to that of
is 7 to 5. Give the measure of
.
The measure of cannot be determine from the information given.
is a diameter, so
is a semicircle, which has measure
. By the Arc Addition Principle,
If we let , then, substituting:
,
and
the ratio of the length of to that of
is 7 to 5; this is also the ratio of their degree measures; that is,
Setting and
:
Cross-multiply, then solve for :
, and
If a secant and a tangent are drawn from a point to a circle, the measure of the angle they form is half the difference of the measures of the intercepted arcs. Since and
are such segments whose angle
intercepts
and
, it holds that:
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