[Stickyelmo]

Hi just had a question of:

The diagram shows a sector OAB of a circle. Centre O and Radius 7cm. Angle AOB = 140.

i) Express 140 in radians.
140/180 = 7/9
7/9pie
ii) Find perimeter of the segment shaded in the diagram giving answer to 3sf.
I can do this but I got it wrong like a billion times before because I did it in radians instead of degrees. Why should I use degrees for part ii yet the first part is about radians 0.0

[raheem94]

(Original post by Stickyelmo)
Hi just had a question of:

The diagram shows a sector OAB of a circle. Centre O and Radius 7cm. Angle AOB = 140.

i) Express 140 in radians.
140/180 = 7/9
7/9pie
ii) Find perimeter of the segment shaded in the diagram giving answer to 3sf.
I can do this but I got it wrong like a billion times before because I did it in radians instead of degrees. Why should I use degrees for part ii yet the first part is about radians 0.0

First of all, learn the difference between 'pi' and 'pie'.

It would have been better had you attached the diagram.

Remember, if you use the formula, , then you need to use radians, but if you use the formula, , then you need to use degrees.

[Bobifier]

You should get the same answer regardless of what units you use. What calculation did you perform to find the perimeter? At some point you will have had to take the angle of the segment divided by the total angle of a circle (that is to say, 2pi radians or 360 degrees), and my guess is that you used radians for part of this and degrees for the other.

[raheem94]

(Original post by Bobifier)
You should get the same answer regardless of what units you use. What calculation did you perform to find the perimeter? At some point you will have had to take the angle of the segment divided by the total angle of a circle (that is to say, 2pi radians or 360 degrees), and my guess is that you used radians for part of this and degrees for the other.

Can you justify the neg rep you gave me?

What was wrong in my post?

[Stickyelmo]

I did it with radians but didn't get the right answer.
to find ab I did 7/sin20 = ab/sin40. Using degrees you get the right answer but with radians you get a different one.

[raheem94]

(Original post by Stickyelmo)
I did it with radians but didn't get the right answer.
to find ab I did 7/sin20 = ab/sin40. Using degrees you get the right answer but with radians you get a different one.

Your calculator should be radians, when you input angles in radians.

Was you calc in radians?

[SubAtomic]

(Original post by raheem94)
Can you justify the neg rep you gave me?

What was wrong in my post?

Maybe he supports Man City

[raheem94]

(Original post by SubAtomic)
Maybe he supports Man City

Supporting Man City doesn't means giving a -7 without justification.

You can see his profile and you will find many visitor messages, where people are asking him why he gave them neg rep.

If someone disagrees with someone's post, then he should at least tell him his mistake, rather than just negging without explaining the problem.

[Brit_Miller]

(Original post by raheem94)
Supporting Man City doesn't means giving a -7 without justification.

You can see his profile and you will find many visitor messages, where people are asking him why he gave them neg rep.

If someone disagrees with someone's post, then he should at least tell him his mistake, rather than just negging without explaining the problem.

"First of all, learn the difference between 'pi' and 'pie'."

Probably that - not everybody likes seeing/having spelling mistakes corrected.

[raheem94]

(Original post by Brit_Miller)
"First of all, learn the difference between 'pi' and 'pie'."

Probably that - not everybody likes seeing/having spelling mistakes corrected.

Many people think that is spelled as 'pie' so i though i should correct this mistake.

A person should know the spelling of such a common word, or if he doesn't know then the other person should try to correct him.

Am i wrong?
I think i should have corrected it, and that -7 was undeserved.

[goape]

steak & kidney pi
pie = 3.1415....

[SubAtomic]

The difference between pi and pie.

pi

Spoiler:

Show

and pie, this may confuse some so be very careful how you interpret this

Spoiler:

Show

[Brit_Miller]

(Original post by raheem94)
Many people think that is spelled as 'pie' so i though i should correct this mistake.

A person should know the spelling of such a common word, or if he doesn't know then the other person should try to correct him.

Am i wrong?
I think i should have corrected it, and that -7 was undeserved.

Oh I'm not saying you're wrong to do so, I gave you +rep 'cause I think it's stupid people negative repping for things like that, but I see it quite often on TSR, unfortunately.

[raheem94]

(Original post by SubAtomic)
Know what you are saying mate, TSR is a funny place, having seen a few of the posts of 4 and 5+ gem rep folk and I wonder how some of them got there. Some have earned it some haven't undoubtedly, TenofThem, Notnek, Farhan, Mr M, Nudaoi, Hassi etc etc are big helps in the maths forums so can understand how they have earned their rep.

You just have to think mate, rep on here is worth nothing in the big bad world. You are on here all the time busting your balls texing stuff and showing methods for all kinds of stuff so you a good dude giving up YOUR personal time to help others understand

I know rep isn't everything. But it does feel disgusting when you get a neg rep without any justified reason and especially from a person who has 7rep gems, and is an experienced member of the forum.

[Stickyelmo]

hehe i dont really care if it is pi or pie since you understood me

this is really helpful. Thanks again tsr!

Remember, if you use the formula, , then you need to use radians, but if you use the formula, , then you need to use degrees.

[raheem94]

(Original post by Brit_Miller)
Oh I'm not saying you're wrong to do so, I gave you +rep 'cause I think it's stupid people negative repping for things like that, but I see it quite often on TSR, unfortunately.

Thanks mate.

[JulietheCat]

Mmm, I'm now craving for a pie. Thanks for the pie picture!