Two students threw a paper plane towards the bin, hitting a desk at time t=10. The trajectory can be modeled as follows:

x=t-2sin(t), y=4-3cos(t)

Then there were a few simple questions before this one:

The students are curious about what would have happened to the paper plane if it had not been obstructed. By repeating the trajectory for different lengths of impact (e.g. 10 metres, 20 metres etc.) find a general expression to indicate the time of impact of the plane for student heads at 10 metre intervals.

I found what y was when t=10, then found heaps of values for t when y was at that height (the height of the obstruction) using co-terminal angles… not sure whether this is right or not, but I have no idea what to do now.

Many thanks for any help.