# Find tangent points in a circle from a point [duplicate]

Circle center : Cx,Cy

Circle radius : a

Point from which we need to draw a tangent line : Px,Py

I need the formula to find the two tangents (t1x, t1y) and (t2x,t2y) given all the above.

## marked as duplicate by Leucippus, Alexander Gruber♦Apr 22 '18 at 18:25

• Hint $(x-x_c)^2+ (y-y_c)^2=a^2$ you need to format using mathjax and show what you have done so far. – Karl Apr 22 '18 at 18:08
Given that $$(x-x_c)^2+(y-y_c)^2=r^2$$ and a point $$P(x_0,y_0)$$ then the line through this point is given by $$y=m(x-x_0)+y_0$$ plug this in the equation of the circle to determine $m$
• this is an equation of a circle with the centre $x_c,y_c$ – Dr. Sonnhard Graubner Apr 22 '18 at 18:25