1. ## Equation Help

Hey guys first post here I'm a j2me developer using some maths for my weather application.

I'm trying to calculate the time of sunrise using this equation:

cos(ωo) = -tan(φ)×tan(δ)

this can be found at [link] Sunrise equation - Wikipedia, the free encyclopedia [/link] aswell as some other places

I know once I have ωo I can find the sunrise however, I dont understand the cos(ωo) bit. I just want the equation in the form

ωo = . . . .

any ideas how I factor out the cos()? I did try and do some inv cos functions but to no avail, any help much appreciated.

2. Originally Posted by blundell
Hey guys first post here I'm a j2me developer using some maths for my weather application.

I'm trying to calculate the time of sunrise using this equation:

cos(ωo) = -tan(φ)×tan(δ)

this can be found at [link] Sunrise equation - Wikipedia, the free encyclopedia [/link] aswell as some other places

I know once I have ωo I can find the sunrise however, I dont understand the cos(ωo) bit. I just want the equation in the form

ωo = . . . .

any ideas how I factor out the cos()? I did try and do some inv cos functions but to no avail, any help much appreciated.
If you have $\displaystyle \cos x = a$ (and $\displaystyle |a|\leq 1$) then it means $\displaystyle x = \cos^{-1} a$ is one such solution. And all solutions are given by $\displaystyle \pm \cos^{-1} a + 2\pi n$.