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Title: Quick Maths Question Post by: bobAlike on February 14, 2013, 09:59:05 PM If a segment of a circle has an area of 4500mmsquared and a radius of 60mm, what's the formula to work out the central internal angle?
TIA Title: Re: Quick Maths Question Post by: technolog on February 14, 2013, 10:03:41 PM You've got the radius so you can calculate the complete circle's area. The ratio of the sector's area to the circle's area is the ratio of the sector's internal angle to 360°.
I think :) Title: Re: Quick Maths Question Post by: outragous76 on February 14, 2013, 10:05:02 PM 142.92 degrees
weird numbers btw - what is it? Title: Re: Quick Maths Question Post by: bobAlike on February 14, 2013, 10:07:52 PM Cheers, its my lads homework. I could work out area of the circle but couldn't workout the internal angle from the info we got
Title: Re: Quick Maths Question Post by: bobAlike on February 14, 2013, 10:09:08 PM What would the formula be. Looked online but doesn't make much sense.
Title: Re: Quick Maths Question Post by: technolog on February 14, 2013, 10:09:27 PM α= sector area / circle area x 360°
Title: Re: Quick Maths Question Post by: outragous76 on February 14, 2013, 10:11:49 PM well i got the area as
Area = 60*60*3.142 = 11,311.2 Known area 4200 as total % of circle = 4200/11311.2*100 = 37.17% so 37.17% of 360 degrees = 360*0.3717 = 133.812 (hmmmmm i rounded in 1st attempt i think) starting to think there is a solid chance im wrong! wait, seen my error...................... Title: Re: Quick Maths Question Post by: bobAlike on February 14, 2013, 10:14:21 PM Area of segment is 4500 Guy. So you were right first time.
Thank you very much peeps Title: Re: Quick Maths Question Post by: outragous76 on February 14, 2013, 10:15:10 PM 60*60*3.14 = 11,304
4500/11304*100 = 39.8% 360*0.398 = 143.28 degrees (i think) Title: Re: Quick Maths Question Post by: outragous76 on February 14, 2013, 10:15:45 PM depends on how many decimal places you take pi to, and whether you "round" during the process
Title: Re: Quick Maths Question Post by: bobAlike on February 14, 2013, 10:16:39 PM 143 is close enough. Thanks again.
Title: Re: Quick Maths Question Post by: celtic on February 14, 2013, 10:30:44 PM Title: Re: Quick Maths Question Post by: nirvana on February 15, 2013, 12:18:12 AM Yep Title: Re: Quick Maths Question Post by: kinboshi on February 15, 2013, 09:55:54 AM α= sector area / circle area x 360° This is the formula I use when working out how big my first slice of pizza needs to be. FYP Title: Re: Quick Maths Question Post by: bobAlike on February 15, 2013, 09:58:34 AM α= sector area / circle area x 360° This is the formula I use when working out how big my first slice of pizza needs to be. FYP I hate to disagree with you Kin but you are wrong his first slice of pizza is allways 360 degrees and so are the second and third. Title: Re: Quick Maths Question Post by: kinboshi on February 15, 2013, 09:59:51 AM α= sector area / circle area x 360° This is the formula I use when working out how big my first slice of pizza needs to be. FYP I hate to disagree with you Kin but you are wrong his first slice of pizza is allways 360 degrees and so are the second and third. That's fair enough. Blame celtic, it was his poor maths ;) |