3. The following definite integrals can be computed exactly without knowing an antiderivative of arctan x. The point is to interpret the given definite integral as signed area and then to either use symmetry or slicing with horizontal strips to arrive at a different definite integral that is easy to evaluate. (a) arctan x dx. -2 ( b ) Jo arctan x dx. (Make sure your answer agrees with the answer to Problem Set 0, #3(e).)