Math Is Fun Forum

Jonny The Multiplier Sum

Guest

Dividing?

Last week i had the strangest dream where i was in math class and i got my test and i thought that we were studying the sine and cosine but we had been doing tangent all week and i couldnt believe my eyes when i took out my calculator and the tangent button wasnt there and i would have to do it all in my head. i know the basic 30 60 90 angles but when it gets down to 57 or 42 i am at a loss. well i woke up in a cold sweat and went down to my mom and dads room and we took out the flashcards one more time so i could really get some practice in. well i hope this helps everybody with their studies

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Dividing?

Cool dream!  Also if just your cosine button works, you can get the sine or tangent from them, if you know how.
Some people like to memorize the formula, and I half do that, plus use a diagram of a circle to help figure out if I subtract or add 90 degrees to get the sign right.
But if only your tangent button works, and the sine and cosine don't, then, well I'll work on that and get back to you...

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igloo myrtilles fourmis

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Dividing?

This might be wrong, but this is just a quick try.
If only your tangent button is working and the square root button works, then maybe:

sin = tan / √(tan² + 1)

and perhaps

cos = 1 / √(tan² + 1)

, but if I'm wrong, I'm sorry.

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igloo myrtilles fourmis

Matthew

Guest

Re: Dividing?

hmm, just testing on my calc, i think you maybe wrong...

Although you could just remember your trigometric Identities..

which are
SinX /CosX  = TanX
(SinX)² + CosX²  = 1

where X is some angle.

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,420

Re: Dividing?

Testing John's identities.....
sin = tan / √(tan² + 1)

cos = 1 / √(tan² + 1)

Both the identities given by John are correct!

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Dividing?

Heh, funny story.  My initials are RHS, and the first time I saw that abbreviation used was in computer science in high school doing operator overloading.  The code was given to me by my teacher and I was trying to figure out why she used my initials for about 10 minutes before I realized it also stood for right hand side.

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."