Math Problem Statement

Find the equation of the tangent line to the hyperbola (x^2/a^2) - (y^2/b^2) = 1 at the point (x0, y0).

Solution

To solve this problem, we need to determine the equation of the tangent line to the hyperbola:

x2a2y2b2=1\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1

at the point (x0,y0)(x_0, y_0). Here's the process:

Step 1: Implicit Differentiation

We start by differentiating the given equation implicitly with respect to xx:

ddx(x2a2)ddx(y2b2)=ddx(1)\frac{d}{dx} \left( \frac{x^2}{a^2} \right) - \frac{d}{dx} \left( \frac{y^2}{b^2} \right) = \frac{d}{dx}(1)

This gives:

2xa22yb2dydx=0\frac{2x}{a^2} - \frac{2y}{b^2} \frac{dy}{dx} = 0

Simplify to solve for dydx\frac{dy}{dx}:

dydx=xa2yb2=b2xa2y\frac{dy}{dx} = \frac{\frac{x}{a^2}}{\frac{y}{b^2}} = \frac{b^2 x}{a^2 y}

So, the slope of the tangent line (mm) is:

m=dydx=b2x0a2y0m = \frac{dy}{dx} = \frac{b^2 x_0}{a^2 y_0}

Step 2: Equation of the Tangent Line

The equation of a line is given by the point-slope form:

yy0=m(xx0)y - y_0 = m (x - x_0)

Substitute m=b2x0a2y0m = \frac{b^2 x_0}{a^2 y_0}:

yy0=b2x0a2y0(xx0)y - y_0 = \frac{b^2 x_0}{a^2 y_0} (x - x_0)

Simplify:

yy0=b2x0xa2y0b2x02a2y0y - y_0 = \frac{b^2 x_0 x}{a^2 y_0} - \frac{b^2 x_0^2}{a^2 y_0}

Reorganize to get:

b2x0xa2y0y+y0=b2x02a2y0\frac{b^2 x_0 x}{a^2 y_0} - y + y_0 = \frac{b^2 x_0^2}{a^2 y_0}

This is the equation of the tangent line.


Would you like further clarification or assistance? Here are some related questions you might want to explore:

  1. How do you compute the slope for tangents to other conic sections (e.g., ellipses)?
  2. What happens to the tangent equation when the point (x0,y0)(x_0, y_0) is a vertex of the hyperbola?
  3. Can you derive the tangent equation for a hyperbola in rotated coordinates?
  4. How does the equation change for a horizontal or vertical hyperbola?
  5. What are the key differences between tangents to hyperbolas and ellipses?

Tip: Always simplify the equation of the tangent line to make it easier to interpret and use in related problems.

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Math Problem Analysis

Mathematical Concepts

Hyperbolas
Implicit Differentiation
Tangent Lines
Calculus

Formulas

\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1
dy/dx = \frac{b^2 x}{a^2 y}
y - y_0 = m (x - x_0)

Theorems

Implicit Differentiation Theorem
Equation of the Tangent Line

Suitable Grade Level

Grades 11-12