Basically there is this graph with the equations:
x = cos t + 2 sin t and y = sin 2t (o<t<pi)
I am asked to find the x-co-ordinates of A, B and D. All these points cross the x-axis, therefore y=0.
How do I go about this?
We do not see the points A, B and D, so a description would be appreciated.
In any case, a point cannot "cross" an axis, a line can. Did you mean line AB and BD cross the x-axis?