The question of finding the tangent line to a graph, or the tangent line problem, was one of the central questions leading to the development of calculus in the 17th century.
So this is line AC, tangent to circle O at point C. Subtract 9 from both sides, and you get x squared is equal to So x squared plus 9 is equal to And so it should jump out at you that x is going to be equal to 4.
It's the distance between the center of the circle and a point on the circle, just like the distance between O and C. Roberval discovered a general method of drawing tangents, by considering a curve as described by a moving point whose motion is the resultant of several simpler motions.
In convex geometrysuch lines are called supporting lines. And so now we are able to figure out that the hypotenuse of this triangle has length 5. It's the side opposite the degree angle. But the thing that might jump out in your mind is OB is a radius.