Let ï(x, y) = arctan(y/x) .(a) find the vector field f = âï, and simplify its components as much as possible.(b) what is the domain of definition of f? (c) find all the points (a, b) (belonging to the domain of definition of f) at which the vector f(a, b) is parallel to the line y = x.

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 0 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)