What is the degree of the differential equation of all circles touching both the coordinate axes in the first quadrant?

What is the differential equation of $\rm y = A- \frac{B}{x}$?

What is $\rm \int^\pi _0 ln\left(tan\frac{x}{2}\right) dx$ equal to?

Where does the tangent to the curve y = e^x at the point (0, 1) meet x-axis?