MathDB
Today's calculation of Integral 193

Source: Tokyo Institute of Technology entrance exam 2007, Problem 2

March 11, 2007
calculusintegrationconicsparabolageometrylimitanalytic geometry

Problem Statement

For a>0a>0, let ll be the line created by rotating the tangent line to parabola y=x2y=x^{2}, which is tangent at point A(a,a2)A(a,a^{2}), around AA by π6-\frac{\pi}{6}. Let BB be the other intersection of ll and y=x2y=x^{2}. Also, let CC be (a,0)(a,0) and let OO be the origin. (1) Find the equation of ll. (2) Let S(a)S(a) be the area of the region bounded by OCOC, CACA and y=x2y=x^{2}. Let T(a)T(a) be the area of the region bounded by ABAB and y=x2y=x^{2}. Find limaT(a)S(a)\lim_{a \to \infty}\frac{T(a)}{S(a)}.