Math Is Fun Forum

Jasonplans

Member

From: US

Registered: 2021-05-26

Posts: 1

Areas of Polygons!

I solved these questions using a different formula from the one taught in the lesson because I didn't know how to use it.
And my teacher wants me to use the one taught in the lesson.

The answers are all correct, she just wants me to use this formula; 5 * (area of triangle).

3. A regular pentagon with a side of 3 centimeters                     
                           
                           A = 1/4 √5 ( 5 + 2√5 ) a^ 2
15.48 sq cm.        A = 1/4 √5 ( 5 + 2√5 ) 3^ 2 ~ 15.4843

4. A regular hexagon with a side of 10 cm
                              A = 3√3/2 a^2
259.81 sq cm.                3√3/2 10^2 ~ 259.81

5. A regular heptagon with a side of 7 inches.

178.06 sq in.   
                           A = 7/4 a^2 Cot (180/7)
                                7/4 7^2 Cot (180/7) ~ 178.06

Bob

Administrator

Registered: 2010-06-20

Posts: 10,580

Re: Areas of Polygons!

hi Jasonplans

Welcome to the forum.

Most teachers would accept an equivalent method as satisfactory.  If this is CompuHigh the I think I know why the teacher wants the taught method.  I did this for someone here:

http://www.mathisfunforum.com/viewtopic.php?id=24102

at post #13.

There are earlier threads on this worksheet but I cannot find them now.  The forum was recently switched to a new server to improve functionality.  Unfortunately there are still some bugs to iron out, one of which is that the search facility doesn't go all the way back.

I'll see if I can find a way for you.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob