let our curve be given by .

note that the line we want is the line passing through the point (1,0,1) with direction vector given by .

now we are concerned with when (since in that case, x = 1, y = 0 and z = 1, hence we are passing through the point (1,0,1))

So, you want the line passing through (1,0,1) that has direction vector

i trust you can take it from here