# Equations of tangent and normal to a curve

• January 7th 2008, 04:59 PM
chibiusagi
Equations of tangent and normal to a curve
I'm lost on the sequence of doing this

Find the tangent and normal to the curves at the points indicated
y=2x^2-4x+1 where the gradient is 4
• January 7th 2008, 05:04 PM
Jhevon
Quote:

Originally Posted by chibiusagi
I'm lost on the sequence of doing this

Find the tangent and normal to the curves at the points indicated
y=2x^2-4x+1 where the gradient is 4

ok, so we know that the gradient of the normal line is -1/4. so let's tuck that away to use it later.

we are concerned with the point where $f'(x) = 4$, find that point. when you have that point, you can find the two lines using the point-slope form:

$y - y_1 = m(x - x_1)$

where $m$ is the slope of the line (m is 4 for the tangent and -1/4 for the normal) and $(x_1,y_1)$ is a point where the line passes through, namely, the point i asked you to find. now continue