Find the equations of the tangent lines to x2+y2=1 at x=0, x=1 and x=35.

Assuming the equation is x^2 + y^2 = 1, then that's a circle, with radius 1, centered on the origin [0,0].

So there are two tangents at x = 0. They are y = 1, and y = - 1 (horizontal lines).

There is one tangent at x = 1. It is x = 1 (a vertical line).

There is no tangent at x = 35, because the original equation has no solution at x = 35.