# how to convert decimal to fraction on calculator?

• Feb 3rd 2008, 11:44 AM
algebra2
how to convert decimal to fraction on calculator?
i entered $cos (\frac{\pi}{6})$ in my calculator and the answer was $0.8660254038$. the book's answer is $\frac{\sqrt{3}}{2}$.

i also did >Frac on my calc and it just showed the decimal form again, not the fraction form. is there a way to transform the decimal answer into the fraction answer?
• Feb 3rd 2008, 11:54 AM
janvdl
Quote:

Originally Posted by algebra2
i entered $cos (\frac{\pi}{6})$ in my calculator and the answer was $0.8660254038$. the book's answer is $\frac{\sqrt{3}}{2}$.

i also did >Frac on my calc and it just showed the decimal form again, not the fraction form. is there a way to transform the decimal answer into the fraction answer?

Yes, IF you have what is called a "Natural/Textbook Display Calculuator". :)

On my Casio fx-82ES there's a button in the middle of the calculator, shown as "S <- -> D" which is used to convert it.
• Feb 3rd 2008, 12:21 PM
algebra2
i have a new black, rare, limited edition TI-84 plus. there are only 100 of them in the world, but i am guessing it's not a natural textbook display calculator...
• Feb 3rd 2008, 02:03 PM
TrevorP
I don't know TI-84s can do that kind of fraction. They only deal with fractions of integers/natural numbers.
• Feb 3rd 2008, 04:49 PM
LordHz
What calculator do you have? The only calculators that can produce a fraction like that are (that I'm aware of) TI-89 or higher.
• Feb 3rd 2008, 05:01 PM
Jhevon
Nevertheless, things like $\cos \frac {\pi}6$ are things you should know.

you should know the value of trig functions at: $0, ~ \frac {\pi}6, ~ \frac {\pi}4, ~\frac {\pi}3, ~\frac {\pi}2, ~\pi$ and any integer multiple of those, and even any 1/2-multiple of those

for other regular fractions, those with no irrational numbers in them, your calculator should be able to handle it

there are memory techniques for memorizing the value of the trig functions of these special angles, so if that's what you're trying to avoid by using your calculator, it's not necessary