3. (1 Point) Match the following equations with the shape of its graph: (a) r = 2, in polar coordinates O Circle O Vertical Line O Horizontal Line O Cone O Sphere O Plane O None of These (b) r =2, in cylindrical coordinates O Circle O Vertical Line O Horizontal Line O Cone O Sphere O Plane O None of These (c) r = sec (0), in polar coordinates O Circle O Vertical Line O Horizontal Line O Cone O Sphere O Plane O None of These (d) p = sec (0), in spherical coordinates O Circle O Vertical Line O Horizontal Line O Cone O Sphere O Plane O None of These 4. (2 Points) Consider the curve defined by the equations x2 + y2 - 2x = 0 with y 2 0. (a) Show that this equation defines a half-circle. (Hint: Complete the square in x). (b) Convert this to an equation in polar coordinates. Give your answer in the form r = f(0). (c) Give an interval for 0 that will trace out this curve, starting at the point (2, 0) and ending at the origin. (Hint: A graph of the circle, and thinking about the radius as a function of the polar angle will be very important here)