Posted by **Kelly** on Saturday, June 28, 2008 at 9:44pm.

if the tangent of two intersecting circles, at their points of intersection are perpendicular, the circles are said to be orthogonal.

Show that the circles x^2+y^2-6x+4y+2=0 and x^2+y^2+8x+2y-22=0 are orthogonal.

find the equation of the tangent to the ellipse x^2/a^2 + y^2/b^2 =1 at the point (a cos theta, b sin theta)

show that the equation of the tangent to the ellipse x^2/a^2 + y^2/b^2 =1 at the point (x1, y1) is xx1/a^2 + yy1/b^2 = 1.

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