\
The parabola is
.
The both tangents to the parabola intersect on
axis are orthogonal .
From the point of symmetry, the lines make angle of
with positive and negative
axis respectively.
Therefore we can assume the points of tangency as
and
.
Slope of the tangent line is derivative of the curve.
\
Differentiate on each side with respect to
.

Find the slope at
.
.
Find the slope at
.
.
The two tangents are perpendicular to each other,so the product of their slopes is
.

Substitute above value in the points
and
.
The points of tangency are
and
.
Find the equation of tangent line
:
Slope at
:
.
Point -slope form of line equation:
.
Substitute
and point
in the above formula.

Find the equation of tangent line
:
Slope at
:
.
Point -slope form of line equation:
.
Substitute
and point
in the above formula.

Compare both tangent line equations with slope-intercept form
.
intercepts of these two lines are
and
.
Thus the point of intersection on
axis is
.
Graph:
\Graph of the parabola.
\Graph the tangent line equations.
\.gif\")
Observe the graphs.
\The tangent lines intersect on
axis at
.
\
Graph of the parabola with tangents intersecting on
axis.
.