Originally Posted by

**MaverickUK82** **Hi Guys!**

I am new to this forum, this being my first ever post.

**The problem:**

I have a problem with calculating the period of a sine curve.

I know the answer to the question - I know how to solve it (or so I thought) but the answer I arrive at doesn't match the one I know (think?!) is right.

I was hoping somebody could guide me through to get the answer I'm looking for?

**The question:**

Involves finding the period for the function:

**h = 35 + 25sin(36t-90)**

The h is relative to the height.

The t is relative to time in minutes.

The function is a model of a fairground big-wheel turning.

I have plotted this on a graph and have found the time it takes for the big wheel to do one revolution is 10 minutes.

I thought the formula to calculate the period from the above was:

**T=((2*pi)/36) = 0.174533**

But how can that be the period when I know from my graphs etc that it takes 10 minutes to do one revolution?

I then thought the 0.174533 might be the frequency, but the reciprocal of the frequency should be period (I'm right on that - right?), but the reciprocal of 0.174533 is 5.73.

I have been on this for over 2 days now, almost non-stop and can't fathom it out. The closest I can get is by multiplying my answer 0.174533 by 60 to get 10.47.

This has really got me wound up - please help!