GMAT Math : DSQ: Calculating an angle in a polygon
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Example Questions
Example Question #11 : Dsq: Calculating An Angle In A Polygon
A nonagon is a nine-sided polygon.
Is Nonagon 
Statement 1:
Statement 2:
EITHER statement ALONE is sufficient to answer the question.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
Each angle of a regular nonagon measures
Therefore, each of the two statements proves that the nonagon is not regular.
Example Question #14 : Polygons
What is the measure of 
Statement 1:
Statement 2:
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
An exterior angle of an equilateral triangle measures 
Example Question #267 : Data Sufficiency Questions
Note: Figure NOT drawn to scale.
Refer to the above figure. Is Pentagon 
Statement 1:
Statement 2:
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
If a shape is regular, that means that all of its sides are equal. It also means that all of its interior angles are equal. Finally, if all of the interior angles are equal, then the exterior angles will all be equal to each other as well.
In a regular polygon, we can find the measure of ANY exterior angle by using the formula
where 
Each exterior angle of a regular (five-sided) pentagon measures
Statement 1 alone neither proves nor disproves that the pentagon is regular. We now know that one exterior angle is 
Statement 2, however, proves that the pentagon is not regular, as it has at least one exterior angle that does not have measure 
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