Why did they plug in 1 for s?

4. (10 points) The parameterized curves a(t) = (3t, t2 - 2, et + 1) and b(s) = ($2 - s, -2s, 83 + $2) intersect at the point P = (0, -2, 2). Find the cosine of the (acute) angle of their intersection at P. Inspecting the first coordinate , P= a ( 0 ) Inspecting the second coordnate, P= 6 ( 1 ). The velocities at P are : a (o) =