# Calculus

• May 23rd 2009, 01:11 PM
gabby
Calculus
What is the equation for the tangent line of a circle with the point on the circle (-1, 2). center of circle (2, -1). i just cant remember the formula. thanks.(worried)
• May 23rd 2009, 02:03 PM
skeeter
Quote:

Originally Posted by gabby
what is the equation for the tangent line of a circle with the point on the circle (-1, 2). center of circle (2, -1). i just cant remember the formula. thanks.

slope of the radius connecting the center of the circle to the point on the circle ...

$m_r = \frac{2-(-1)}{-1-2} = -1$

slope of the tangent line is the opposite reciprocal of $m_r = -1$ ...
$m_T = 1$

tangent line equation ...

$y - 2 = 1[x - (-1)]$