Consider the 2-sphere with the metric
ds^2 = gabdx^adx^b = a^2((dr^2)/(1-r^2) + r^2dθ^2)
where a is a constant with length dimensions, 0 <= θ < 2π and 0 <= θ < 2π.
a. Make a drawing of each of the coordinate curves
b. Show that with this coordinate system it is not possible to cover the entire surface of the 2-sphere.