59. The straight line joining the middle point of the hypotenuse of a right-angled triangle to the right angle is equal to half the hypotenuse,
60. From the angle A of a triangle ABC a perpendicular is drawn to the opposite side, meeting it, produced if necessary, at D; from the angle B a perpendicular is drawn to the opposite side, meeting it, produced if necessary, at D shew that the straight lines which join D and E to the middle point of AB are equal.
61. From the angles at the base of a triangle perpendiculars are drawn to the opposite sides, produced if necessary: shew that the straight line joining the points of intersection will be bisected by a perpendicular drawn to it from the middle point of the base.
62. In the figure of I. 1, if C and H be the points of intersection of the circles, and AB be produced to meet one of the circles at E, shew that CHK is an equilateral triangle.
63. The straight lines bisecting the angles at the base of an isosceles triangle meet the sides at D and E: shew that DE is parallel to the base.
64. AB,AC are two given straight lines, and P is a given point in the former: it is required to draw through P a straight line to meet AC at Q, so that the angle APQ may be three times the angle AQP.
65. Construct a right-angled triangle, having given the hypotenuse and the sum of the sides.
66. Construct a right-angled triangle, having given the hypotenuse and the difference of the sides.
67. Construct a right-angled triangle, having given the hypotenuse and the perpendicular from the right angle on it.
68. Construct a right-angled triangle, having given the perimeter and an angle.
69. Trisect a right angle.
70. Trisect a given finite straight line.
71. From a given point it is required to draw to two parallel straight lines, two equal straight lines at right angles to each other.
72. Describe a triangle of given perimeter, having its angles equal to those of a given triangle.
