Tangents are drawn to `x^2 + y^2 = 1` from any arbitrary point `P` on the circle `C_1 : x^2 + y^2 - 4 = 0.` These tangent meets the circle `'C_1'` again in `A` and `B`. Locus of point of intersection of tangents drawn to `C_1,` at `A` and `B`