MathDB
Today's calculation of Integral 564

Source: 2010 Tokyo Univesity entrance exam/Science, Problem 4

February 25, 2010
calculusintegrationanalytic geometryfunctiongeometrylogarithmscalculus computations

Problem Statement

In the coordinate plane with O(0, 0) O(0,\ 0), consider the function C: \ y \equal{} \frac 12x \plus{} \sqrt {\frac 14x^2 \plus{} 2} and two distinct points P1(x1, y1), P2(x2, y2) P_1(x_1,\ y_1),\ P_2(x_2,\ y_2) on C C. (1) Let H_i\ (i \equal{} 1,\ 2) be the intersection points of the line passing through P_i\ (i \equal{} 1,\ 2), parallel to x x axis and the line y \equal{} x. Show that the area of OP1H1 \triangle{OP_1H_1} and OP2H2 \triangle{OP_2H_2} are equal. (2) Let x1<x2 x_1 < x_2. Express the area of the figure bounded by the part of x1xx2 x_1\leq x\leq x_2 for C C and line segments P1O, P2O P_1O,\ P_2O in terms of y1, y2 y_1,\ y_2.