help me guys!
find the equation of the tangent line at (2,-1) on the circle (x+20)^2+(y+2)^2=25

Question

help me guys! 
find the equation of the tangent line at (2,-1) on the circle (x+20)^2+(y+2)^2=25

anonymous · Answer

hint :
tangent line is perpendicular to the radial line..

anonymous · Answer

y=2x-5
working
tangent is perpendicular to the radius of the circle. 
Gradient at the point (2,-1) from origin (0,0) = -1/2     rise/run or (y1-y2)/(x1-x2)
Since it is perpendicular the gradient of the tangent is equal to the negative reciprocal of the gradient of the circle. Gradient of tangent = 2
so equation 
y=2x+c 
Find c by substituting the values (2,-1)
-1= 2(2)+c
c=-5