I had a quick search on the forums for help on my question and found this

http://www.mathhelpforum.com/math-he...ays-tides.html (also i think i accidently posted this thread in the wrong sub-forum)

However my question is a little different in terms of the placement of "t" and the fact that i'm useless with fractions in equations.

The equation is $\displaystyle 2.5 \sin \left(\frac{\pi t}{12}\right)$

The question in the link is similar but with the placement of the "t" in the equation. I know from my graph and workings that 1.250m occurs at Hours 2, 10, 26 and 34 for 0 ≤ t ≤ 36.

I tried to rearrange the equation for 1.3 by doing:

2.5sin(pi)t/12 = 1.3

sin(pi)t/12 = 0.52

but then i got stuck.

Any inputs or hints pls?