Lesson 10-2 (Part 2): Area of Regular Polygons

What is the formula for area of a regular polygon?

• $A=\frac{1}{2}\cdot a\cdot s\cdot n$

• $A=\frac{1}{2}b\cdot h$

• $A=\pi r^2$

What does the "n" stand for in the formula for area of a regular polygon?

• apothem

• length of one side of the polygon

• number of sides the polygon has

What does the "a" stand for in the formula for area of a regular polygon?

• apothem

• length of one side of the polygon

• number of sides the polygon has

What does the "s" stand for in the formula for area of a regular polygon?

• apothem

• length of one side of the polygon

• number of sides the polygon has

You will be finding the area of a regular octagon with side length 6 km, as shown in the picture. First, What is the measure of the central angle of the octogon?

• 60 $\degree$

• 45 $\degree$

• 30 $\degree$

• 80 $\degree$

What is the correct formula that can be used to find the apothem?

•  $\cos45=\frac{3}{a}$  

•  $\tan45=\frac{3}{a}$  

•  $\tan22.5=\frac{6}{a}$  

•  $\tan22.5=\frac{3}{a}$  

What is value of the apothem? Round your answer to four decimal places.

• 0.1381

• 7.2426

• 3.0000

• 7.2428

What is the area of the regular octagon with side length 6 km?

•  $173.8\ km^2$  

•  $186.5\ km^2$  

•  $584.2\ km^2$  

•  $94.2\ km^2$  

You will be finding the area of a regular nonagon with side length 7 cm, as shown in the picture. First, What is the measure of the central angle of the nonagon?

• 20 $\degree$

• 51.4 $\degree$

• 30 $\degree$

• 40  $\degree$

What is the correct formula that can be used to find the apothem?

• $\tan20=\frac{3.5}{a}$

• $\tan20=\frac{7}{a}$

• $\tan20=\frac{a}{3.5}$

• $\tan40=\frac{7}{a}$