# Thread: Simplifying a trigonometric equation given certain values

1. ## Simplifying a trigonometric equation given certain values

theta= 2*atan(x*tan(alpha /2)/y)

where
alpha = 45 degree
x = 12.5
y = 12.0

i don't know what is the value of "atan". if anyone know then help me....and suggest me any book where i can find the solution....thanks.

2. Originally Posted by mikeani

theta= 2*atan(x*tan(alpha /2)/y)

where
alpha = 45 degree
x = 12.5
y = 12.0

i don't know what is the value of "atan". if anyone know then help me....and suggest me any book where i can find the solution....thanks.
There is no way to solve this exactly, if that's what you mean. As far as "atan" is concerned, the two usual ways of expressing this are "atn" or more commonly $tan^{-1}$. This is the inverse tangent function.

-Dan

3. Originally Posted by mikeani

theta= 2*atan(x*tan(alpha /2)/y)

where
alpha = 45 degree
x = 12.5
y = 12.0

i don't know what is the value of "atan". if anyone know then help me....and suggest me any book where i can find the solution....thanks.
You don't need to "solve" for anything here! It's just a matter of "plug n' chug" into the expression given (the already gave you the values of $\displaystyle \alpha$, x, and y) so you can find $\displaystyle \theta$. And as topsquark said, atan most likely means the inverse tangent function arctan(x), also written as $\displaystyle \tan^{-1}(x)$.

4. Ok...thank you guys...now i get it.