- #1
snshusat161
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Homework Statement
If the equation of one tangent to the circle with center at (2, -1) from the origin is 3x + y = 0, then the equation of the other tangent through the origin is:
(a) 3x - y = 0
(b) x + 3y = 0
(c) x - 3y = 0
(d) x + 2y = 0
Homework Equations
An equation of the tangent to the circle [tex]x^2 +y^2 + 2gx + 2fy + c = 0[/tex] at the point [tex]( x_{1}, y_{1})[/tex] on the circle is
xx1 + yy1 + g(x + x1) + f (y + y1) + c = 0
There are more but I presume that you know
The Attempt at a Solution
I've already solved this question from another method but just asking out of my curiosity.
I've learned it on my lower classes that radius are perpendicular to the tangent of the circle. It means that we must get m1. m2 = -1 but as you can see we are not getting, neither in the case of first tangent nor in the case of second (in any of the option given). Can you tell me, why?