[" The normal to a given curve is "],[" parallel to "x" -axis,if "]

If normal of the curve is parallel to x axis then

Find the point on the curve x^(2) + y^(2)- 4xy + 2= 0 , where the normal to the curve is parallel to the X-axis.

if y=(e^(-ax))(tan x) The tangent at a given point on the curve is parallel to x-axis.Find a.

Write the value of (dy)/(dx) , if the normal to the curve y=f(x) at (x, y) is parallel to y - axis.