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#1 2005-10-14 03:00:29

Math Student
Guest

More help on angles please!

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.

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?

#2 2005-10-14 04:38:43

Math Student
Guest

Re: More help on angles please!

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.

#3 2005-10-14 04:45:39

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: More help on angles please!

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.


Why did the vector cross the road?
It wanted to be normal.

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#4 2005-10-14 05:02:58

Math Student
Guest

Re: More help on angles please!

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

#5 2005-10-14 05:06:08

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: More help on angles please!

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.


Why did the vector cross the road?
It wanted to be normal.

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#6 2005-10-14 05:13:10

Math Student
Guest

Re: More help on angles please!

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

#7 2005-10-14 10:57:05

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,534

Re: More help on angles please!

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


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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