# [SOLVED] Find equations of the tangent line...

• Mar 12th 2009, 11:43 AM
moonman
[SOLVED] Find equations of the tangent line...
Find equations of the tangent line and normal line to the given curve at the specified point.

Y = 2xe^(x) , (0,0)
• Mar 12th 2009, 12:01 PM
Air
Quote:

Originally Posted by moonman
Find equations of the tangent line and normal line to the given curve at the specified point.

Y = 2xe^(x) , (0,0)

A tangent line is a straight line that touches a function at only one point. The slope of the tangent line (the gradient) at a point on the function is equal to the derivative of the function at the same point.

$y=2xe^x$

$\frac{\mathrm{d}y}{\mathrm{d}x} = 2xe^x + 2e^x$. At $(0,0)$, The tangent gradient equals $m = 2(0)e^0 + 2e^0 = 2$

Equation of tangent: $y-0 = 2(x-0) \rightarrow y = 2x$

The equation of Normal line has the same coordinate of intersection $(0,0)$ and the same y-intercept but the gradient is different. The gradient of the normal line is $n = -\frac{1}{m} = -\frac{1}{2}$ where $m$ is the gradient of the tangent line and $n$ is the gradient of the normal line.

This Equation of normal line: $y-0 = -\frac12 (x-0) \rightarrow y = -\frac12 x$