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### Passatges populars

Pŕgina 39 - The line which joins the mid-points of two sides of a triangle is parallel to the third side and equal to one half of it.
Pŕgina 168 - The cycloid. This is the curve traced by a point on the circumference of a circle, when the circle is made to roll (without sliding) on a straight line.
Pŕgina 205 - A PLANE is a surface, such, that if any two of its points be joined by a straight line, such.
Pŕgina 182 - Find the locus of a point the sum of the squares of whose distances from the angular points of a given square is constant.
Pŕgina 75 - PF' = 2 a. 97. Hence, an ellipse may also be defined as the locus of a point the sum of whose distances from two fixed points is constant.
Pŕgina 70 - By definition [§ 69], the ellipse is the locus of a point whose distance from a fixed point, the focus, divided by its distance from a fixed line, the directrix, is a constant e, less than 1. Let F be the focus ,' and SR the directrix. Through F take А' я с A tsFD perpendicular to SR at D. There is a point A between F and D such that FA/AD = e.
Pŕgina 185 - Prove that the locus of the poles of a given line with respect to a system of confocal conies is a line perpendicular to the given line.
Pŕgina 191 - What are the relative positions of the following eight points: (a, b, c), (a, ft, - c), (a, - 6, c), (- a, b, c), (a, - 6, - c), (- a, b, - c), (- a, - 6, c), (- a, - 6, - c) ? Which of these points are symmetric with regard to the origin ? Which are symmetric with regard to the coordinate planes ? 236. Problem. To express the distance between two points P, P", in terms of their coordinates (x1, y', z'), (x", y", z"). Through P' and P" take planes parallel to the coordinate planes.
Pŕgina 22 - Find also the point of intersection of the diagonals. 12. Find the equation of the line which passes through the point (2, — 3) and makes an angle of 60° with the x-axis.
Pŕgina 200 - What are the coordinates of the point of intersection ? 12. Find the coordinates of the mid-point of the line segment joining the points (5, — 2, 7) and (2, 2, — 5); also the coordinates of the points where this line segment is trisected.