A line meets the coordinate axes at `A` and `B` . A circle is circumscribed about the triangle `O A Bdot` If `d_1a n dd_2` are distances of the tangents to the circle at the origin `O` from the points `Aa n dB` , respectively, then the diameter of the circle is `(2d_1+d_2)/2` (b) `(d_1+2d_2)/2` `d_1+d_2` (d) `(d_1d_2)/(d_1+d_2)`