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Topic review (newest first)

MathsIsFun
2005-10-15 08:57:05

A septagon has 7 sides. If it is irregular, then it could have any variation of side lengths and angles.

Math Student
2005-10-15 03:13:10

Thanks for that.

Ermm... do you know how to draw the irregular septagon? I'm still having trouble with it.

Sorry about number 2. It's sometimes hard to show fractions

mathsyperson
2005-10-15 03:06:08

1) Yes, you're right. Sorry.

2) I took 4 (1/2) to mean a strange way of saying 2, so you're right there as well. Sorry again.

Math Student
2005-10-15 03:02:58

There was a mistake with your number 1. 900/8 is 112.5 not 125. I got 112.5 but I can't draw the shape.

For number 2 I got 20?

The bottom two angles are:
4 1/2x +4 1/2x
9x/2 + 9x/2 = 18x/2 = 9x

9x+x = 10x

180 /10=18
therefore
x=18

360/18=20

mathsyperson
2005-10-15 02:45:39

1) A heptagon has (7-2)*180 = 900 degrees totalling its internal angles.
All of the internal angles in this heptagon total 8x. Therefore, x = 900/8 = 125

2) I won't bother explaining because you've done it and the explanation is lengthy, but I got it to be a hexagon. Am I right?

3) The external angles of a polygon always add to 360. The average external angle is (8+12)/2 = 10, so there are 360/10 = 36 sides.

Math Student
2005-10-15 02:38:43

Don't nother wiht munber 2! I've worked that one out.

Oh yes, for number 1 could you draw the shape out for me? I found out that the angle should be 112.5 but I'm not sure if that is right.

Math Student
2005-10-15 01:00:29

1)

A heptagon has 6 equal angles x and one angle 2x. Find the value of x.

2)

PQ is one side of a regualar polygon with centre O.
If y=4 (1/2)x find the number of sides in the polygon.

http://www.webpost.net/he/henrylee/mathsproblem.GIF

3)

Half of the exterior angles of a polygon are 8  and the other exterior angles are each 12 . How many sides has the polygon?

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