High School Math : Plane Geometry

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : How To Find The Area Of A Polygon

Find the area of the shaded region:

7

Possible Answers:

Correct answer:

Explanation:

The formula for the area of the shaded region is

where  is the radius of the circle.

Plugging in our values, we get:

Example Question #2 : How To Find The Area Of A Polygon

Find the area of the following octagon:

20

Possible Answers:

Correct answer:

Explanation:

The formula for the area of a regular octagon is:

Plugging in our values, we get:

Example Question #1 : How To Find The Area Of A Polygon

Find the area of a rectangle with a base of  and a width of  in terms of .

Possible Answers:

none of the other answers

Correct answer:

Explanation:

This problem simply becomes a matter of FOILing (first outer inner last)

The area of the shape is Base times Height.

So, multiplying  and   using FOIL, we get an area of 

Example Question #11 : Plane Geometry

Find the area of a square whose diagonal is .

Possible Answers:

none of these answers

Correct answer:

Explanation:

If the diagonal of a square is , we can use the pythagorean theorem to solve for the length of the sides. 

 = length of side of the square

Doing so, we get 

 

To find the area of the square, we square , resulting in .

Example Question #1 : How To Find An Angle In A Polygon

What is the magnitude of the interior angle of a regular nonagon?

Possible Answers:

Correct answer:

Explanation:

The equation to calculate the magnitude of an interior angle is , where  is equal to the number of sides.

For our question, .

Example Question #12 : Geometry

What is the interior angle measure of any regular heptagon?

 

Possible Answers:

Correct answer:

Explanation:

To find the angle of any regular polygon you find the number of sides, . In this example, .

You then subtract 2 from the number of sides yielding 5.

Take 5 and multiply it by 180 degrees to yield the total number of degrees in the regular heptagon. 

Then to find one individual angle we divide 900 by the total number of angles, 7.

The answer is  .

Example Question #13 : Other Polygons

A regular polygon with  sides has exterior angles that measure  each. How many sides does the polygon have?

Possible Answers:

This figure cannot exist.

Correct answer:

Explanation:

The sum of the exterior angles of any polygon, one per vertex, is . As each angle measures , just divide 360 by 1.5 to get the number of angles.

Example Question #14 : Other Polygons

What is the interior angle measure of any regular nonagon?

Possible Answers:

Correct answer:

Explanation:

To find the angle of any regular polygon you find the number of sides , which in this example is .

You then subtract  from the number of sides yielding .

Take  and multiply it by  degrees to yield a total number of degrees in the regular nonagon.

Then to find one individual angle we divide  by the total number of angles .

 

The answer is .

Example Question #12 : Geometry

What is the measure of one exterior angle of a regular seventeen-sided polygon (nearest tenth of a degree)?

Possible Answers:

Correct answer:

Explanation:

The sum of the measures of the exterior angles of any polygon, one per vertex, is . In a regular polygon, all of these angles are congruent, so divide 360 by 17 to get the measure of one exterior angle:

Example Question #13 : Geometry

What is the measure of one exterior angle of a regular twenty-three-sided polygon (nearest tenth of a degree)?

Possible Answers:

Correct answer:

Explanation:

The sum of the measures of the exterior angles of any polygon, one per vertex, is . In a regular polygon, all of these angles are congruent, so divide 360 by 23 to get the measure of one exterior angle:

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