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Old 30th Sep 2013, 20:09   #1
T345
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How to find the angle of a sector using the area and radius

Hi guys, another maths question.
I am having trouble finding the method to do this, online and in my head.
The question is:
A sector with radius 6cm has an area 70cm sq. Calculate the angle of the sector Theta.
I am struggling, and if anyone can show me how to do it, I will be grateful.
Thanks
Bakht

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Old 30th Sep 2013, 20:15   #2
[FnG]magnolia
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Go to bed homework, you're drunk.

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Old 30th Sep 2013, 20:17   #3
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Go to bed homework, you're drunk.
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Old 30th Sep 2013, 20:18   #4
D.P.
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Quote:
Originally Posted by T345 View Post
Hi guys, another maths question.
I am having trouble finding the method to do this, online and in my head.
The question is:
A sector with radius 6cm has an area 70cm sq. Calculate the angle of the sector Theta.
I am struggling, and if anyone can show me how to do it, I will be grateful.
Thanks
Bakht

The answer is very easy, I will let you work it out form basic principles:
A) What is the formula to find the area of a circle?
b) what is the radius of the circle given in the questions?
C) What is the fractional area of the sector given in the question?
D) If you cut a circle n half what would the area of the 2 half be and what are the angles of the 2 sectors?
E) Out of 360 degrees the sector must have angle with a fraction proportional to the areas.
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Old 30th Sep 2013, 20:34   #5
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Old 30th Sep 2013, 20:35   #6
T345
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Quote:
Originally Posted by D.P. View Post
The answer is very easy, I will let you work it out form basic principles:
A) What is the formula to find the area of a circle?
b) what is the radius of the circle given in the questions?
C) What is the fractional area of the sector given in the question?
D) If you cut a circle in half what would the area of the half be and what are the angles of the 2 sectors?
E) Out of 360 degrees the sector must have angle with a fraction proportional to the areas.
Ok, so I got the area of the entire circle (36pi).
The fractional area would be
70/36pi.
I don't know what you mean in D though

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Old 30th Sep 2013, 20:36   #7
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1.21 Jiggawatts.
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Old 30th Sep 2013, 20:42   #8
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Old 30th Sep 2013, 20:43   #9
Devrij
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Originally Posted by T345 View Post
Ok, so I got the area of the entire circle (36pi).
The fractional area would be
70/36pi.
I don't know what you mean in D though
He's saying half a circle would be 18pi, and the angle of that sector is 180 degrees. So work out what the angle is using the fraction that 77/36pi represents.

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Old 30th Sep 2013, 20:49   #10
Elixir
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Originally Posted by T345 View Post
Ok, so I got the area of the entire circle (36pi).
The fractional area would be
70/36pi.
I don't know what you mean in D though
theta/360 = 70/36pi

The angle will be the same fraction of the entire circle as the area is.
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Old 30th Sep 2013, 20:51   #11
Hyburnate
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Yeah, dude I pity you. Maths goes straight over my head.

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Old 30th Sep 2013, 20:53   #12
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Over 9000.
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Old 30th Sep 2013, 20:56   #13
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42
http://tysonadams.files.wordpress.com/2012/08/42.gif

No hotlinking. Thank you.
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Old 30th Sep 2013, 21:05   #14
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The area of a full circle of radius 6 is 36*pi. Yours isn't a full circle, it has area 70. So the fraction of the circle you have is 70/(36*pi). Multiply that by 360, and you have your answer in degrees. If you want to show off to your maths teacher, give the answer in radians instead.

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Old 30th Sep 2013, 21:28   #15
D.P.
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Quote:
Originally Posted by T345 View Post
Ok, so I got the area of the entire circle (36pi).
The fractional area would be
70/36pi.
I don't know what you mean in D though
Im just trying to get you to think. If you cut a circle in half then each half would have an angle of 180 degrees which is half of 360 and the area of each half is obviously half the original entire circle.

If you understand why that works then it is obvious how the angle of the sector and area relate to the original circle.
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Old 30th Sep 2013, 21:28   #16
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Old 30th Sep 2013, 21:59   #17
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A circle of radius 6cm has an area of pi * 6 * 6 (pi r^2)

The area of the cake slice is 70cm

The proportion of the whole cake (360 degrees) is 360 * 70 / (pi * 36)

Now please tell me that this is year 7 stuff .....

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Old 30th Sep 2013, 23:27   #18
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A circle of radius 6cm has an area of pi * 6 * 6 (pi r^2)

The area of the cake slice is 70cm

The proportion of the whole cake (360 degrees) is 360 * 70 / (pi * 36)

Now please tell me that this is year 7 stuff .....
Year 7 really ?

Why do people always put people down who don't understand math? Not every is great it and believe it or not, some people have little to no time for math, bar say passing it at GCSE level.

Quote:
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I always indicate but only becuase the high quality,
solid feel of my indicator switches turns me on.
Last edited by teaboy5; 30th Sep 2013 at 23:32.
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Old 30th Sep 2013, 23:37   #19
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Originally Posted by teaboy5 View Post
Year 7 really ?

Why do people always put people down who don't understand maths? Not every is great it and believe it or not, some people have little to no time for mathS, bar say passing it at GCSE level.
I really really had to do this. I just did.
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Old 30th Sep 2013, 23:54   #20
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Year 7 really ?

Why do people always put people down who don't understand math? Not every is great it and believe it or not, some people have little to no time for math, bar say passing it at GCSE level.
Gnnnnngggnnggghggggg..... MATHS.. MATHS
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Old 1st Oct 2013, 00:07   #21
d_brennen
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Did someone say meth?


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Old 1st Oct 2013, 04:46   #22
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Did someone say meth?

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Old 1st Oct 2013, 06:01   #23
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Ok so you cut a cake in two and you still have one cake but two halves.

So if you cut a sandwich in half do you have two sandwiches or two half sandwiches?

Please state your working preferably in MS Paint.

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Old 1st Oct 2013, 06:50   #24
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There's this plane on a treadmill, right, and

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Old 1st Oct 2013, 08:29   #25
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My brain hurts just reading this

Please read the rules and FAQ regarding signature sizes why ?, If i get it right.. its wrong! So you get a sig that wont be removed - who did this ?, Show yourself! - It wasn't me!
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Old 6th Nov 2013, 22:14   #26
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I don't miss school y'know.


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Old 6th Nov 2013, 22:19   #27
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Old 6th Nov 2013, 22:25   #28
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what if the cake was a square shaped cake?

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Old 6th Nov 2013, 22:31   #29
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what if the cake was a square shaped cake?
What if the cake didn't actually exist and this question was in fact invalid?

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Old 6th Nov 2013, 22:35   #30
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What if the cake didn't actually exist and this question was in fact invalid?
Whaa?
a minute ago we were talking pie and I was interested and paying attention, now we are talking existential cake?
This is all too fast for me, I'm not that kind of boy
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