# A stupid question.

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• June 15th, 2005, 04:01 AM
pranki
A stupid question.
A question to non-Russians. I've read some article. I don't believe it, but... it really awoke my interest. Strong interest. I know that my doubt may offend you, but I can't suffer any more. Execuse me, if you find my question insulting.

OK, here's the most stupid question I've ever asked:
Do you know why sin30 = 0,5?
• June 15th, 2005, 04:15 AM
saibot
Um...this is a mathematical operation.

The sine (abbreviated "sin") of an angle measurement of 30 degrees is equal to 0.5

sin(30)=0.5

This is the only way I can make sense of that....

• June 15th, 2005, 04:21 AM
kwatts59
sin(30) = 0.5

The sine of a 30 degree angle is 0.5.
That means if you shoot something at a 30 degree angle, the height attained is half of the distance covered. (But that is assuming there is no gravity.) :D
• June 15th, 2005, 04:27 AM
http://www.gcse.com/maths/images/sin30.gif

Because, my friend, when a triangle has the angle of 30 degrees, the hypotenus is double as long as the opposite! ALWAYS! And then the ratio will always be 1/2!

sin X = Opposite / Hypotenus

PS: Opposite is the line which is opposite the angle X and hypotenus is that really long line opposite the 90 deg
• June 15th, 2005, 04:30 AM
saibot
I am impressed with your math skills!
• June 15th, 2005, 04:38 AM
Well, it is kind of my job to know math... :P

Anyway, how do you spell sinus / sine / sin in Russian? Do you use latin letters or what?
• June 15th, 2005, 04:40 AM
saibot
синус
• June 15th, 2005, 04:41 AM
TriggerHappyJack
Ha! That was on my Algebra final this year! SohCahToa! I think, I can't remember. I wrote it on my hand. :roll:
• June 15th, 2005, 04:43 AM
saibot
SohCahToa is what got me through those courses...I can never forget it.
• June 15th, 2005, 04:48 AM
TriggerHappyJack
I miss my Algebra class! I had so much fun there! :lol: Even if I can't really remember much. -Wipes tear-

Edit:
Why am I capitalizing Algebra?
• June 15th, 2005, 05:00 AM
N
Вопрос, видимо, навеян этой статьёй :lol:
http://nauka.relis.ru/05/0412/05412020.htm
• June 15th, 2005, 05:04 AM
pranki
Quote:

sin X = Opposite / Hypotenus
OK, kalinka, what must I do when X > 180? sin270 = -1, but can you give me a triangle with 270 degrees angle? :wink:
• June 15th, 2005, 05:11 AM
pranki
Quote:

Originally Posted by N
Вопрос, видимо, навеян этой статьёй :lol:
http://nauka.relis.ru/05/0412/05412020.htm

You're right!
But just understand, I don't want to offend somebody. The article describes such fantastic things, unbelievable things! So unbelievable for me, that my interest doesn't allow me to be calm!
• June 15th, 2005, 05:19 AM
DDT
Sorry Pranky but when they started to mix numbers with the alphabet they lost me.
• June 15th, 2005, 05:27 AM
Quote:

Originally Posted by pranki
Quote:

sin X = Opposite / Hypotenus
OK, kalinka, what must I do when X > 180? sin270 = -1, but can you give me a triangle with 270 degrees angle? :wink:

Well, ok, this method it only works for < 90 degrees

For larger values... you have to learn... the... dreaded... UNIT CIRCLE (dramatic music)

http://www2.spsu.edu/math/edwards/1113/unit2.gif

Hint: - If you are doing a sine of the angle, look for the intersection from the unit circle's circumfrance to the vertical line (for cosinus to the horizontal line)
• June 15th, 2005, 05:44 AM
pranki
kalinka, you're quite right!!! Now I know, that the article lies!

But let's think about the following. How does your calculator get values of sine? Does it draw the unit circle (thanks for the term, I didn't know how does единичная окружность sound in English) in its memory, look for intersections etc?
• June 15th, 2005, 10:47 AM
Quote:

Originally Posted by pranki
The article describes such fantastic things, unbelievable things! So unbelievable for me, that my interest doesn't allow me to be calm!

What's so unbelievable about it? *Shrug*
• June 15th, 2005, 03:16 PM
laxxy
Quote:

Originally Posted by pranki
kalinka, you're quite right!!! Now I know, that the article lies!

But let's think about the following. How does your calculator get values of sine? Does it draw the unit circle (thanks for the term, I didn't know how does единичная окружность sound in English) in its memory, look for intersections etc?

pranki, do _you_ really know how exactly it gets the values? i suspect it might well depend on the calculator (unless there is one cheap chinese chip that everyone uses)
• June 15th, 2005, 04:34 PM
pranki
Quote:

Originally Posted by laxxy
pranki, do _you_ really know how exactly it gets the values? i suspect it might well depend on the calculator (unless there is one cheap chinese chip that everyone uses)

I just wanted to get the most common definition of sine.

OK, I call off my last question. It isn't fairly, because it is learned in univesity departments, which are dedicated to mathematics, and ordinary people don't have to know this.
I'm sorry.
• June 15th, 2005, 04:37 PM
fantom605
Aah!!! Get this crap out of my face! I had to take 22 semesters of Advanced Algebra / Advanced Calc in school! I've spent years erasing this all from my memory! :lol:
-Fantom

ps- TriggerHappyJack, I have the habit of capitalizing Algebra and Calc also, maybe it's our nature to capitalize things that suck a lot...!
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