Question

find area of regular pentagon.

Answer 1

\[A=1/4\sqrt{5(5+2\sqrt{5)}} a^2\] formula

Answer 2

Area of a regular polygon: (1/2)(length of apothem)(perimeter)

Answer 3

That 12 is the apothem

Answer 4

i got that and is the little a = 12?

Answer 5

the little a is ONE SIDE of the pentagon..

Answer 6

Do they give you length of one side?

Answer 7

no sides given

Answer 8

i think you might be able to find the side length using the apothem

Answer 9

if I do that big formula at the top by chlobohoe I get 20.64

Answer 10

I have to no idea how to get a side, but can't I use the area formula and just substitute a = 12

Answer 11

no you cant babe here is the formula you need first:
\[side=2(apothem)\tan(180/n)\]
where apothem is 12 and n is number of sides

Answer 12

why can't I use the area formula - it doesn't call for a side figure in it?

Answer 13

no hun you use the side formula to figure out the length of ONE SIDE and then plug that into the Area formula. its the a^2 at the end

Answer 14

got it I thought the a^2 in that formula was the 12

Answer 15

so the side = 2(12) * tan(180/5)
= 186.01

Answer 16

umm make sure ur following PEMDAS.
i got s=17.43702067

Answer 17

where does cos, tan & sin fall in the PEMDAS routine?

Answer 18

This will all work, however make sure your calculator is in degrees mode

However another area formula is

\[\large Area = nr^2 \tan(\frac{180}{n})\]
So here
\[\large A = 5\times (12^2) \times \tan(\frac{180}{5})\]

You will get the same answer as if you continue from here

Answer 19

hahahaha its just multiplication lemme show ya