- Home
- Standard 11
- Mathematics
10-2. Parabola, Ellipse, Hyperbola
easy
What is the slope of the tangent line drawn to the hyperbola $xy = a\,(a \ne 0)$ at the point $(a, 1)$
A
$1/a$
B
$-1/a$
C
$a$
D
$-a$
Solution
(b) Given equation of hyperbola $xy = a$
Slope of tangent at point $({x_1}\,{y_1})$ is
$m = {\left( {\frac{{dy}}{{dx}}} \right)_{({x_1},\,{y_1})}}$
$\therefore \,\frac{{xdy}}{{dx}} + y = 0$
==> $\frac{{dy}}{{dx}} = \frac{{ – y}}{x}$
At point $(a,\,1);$ $m = {\left( {\frac{{dy}}{{dx}}} \right)_{(a,\,1)}} = – \frac{1}{a}$.
Standard 11
Mathematics