Suppose that curves C1 and C2 intersect at (x0, y0) with slopes m1 and m2, respectively, as in Figure 4. Then (see Problem 40 of Section 0.7) the positive angle θ from C1 (i.e., from the tangent line to C1 at (x0, y0)) to C2 satisfies
tan θ = m2 - m1 / 1 + m1m2

Find the angles from the circle x2 + y2 = 1 to the circle (x - 1)2 + y2 - 1 at the two points of intersection.