...B + ft cos3 B + 7 cos C sin2 B) (aa + i0 + C7). 3. To find the equation to the circle described on the line joining the middle points of two sides of a triangle. Let D, F (Fig. 3) be the middle points of BC, BA; join DF and draw the perpendiculars DH, FK. Then...

...is equal to three times that in the first. VL 119. The line joining the points of bisection of any two sides of a triangle is parallel to the third side, and the triangle so formed is onefourth of the given triangle. 120. If in the triangle ABC, BC be bisected...

...same point and cut each other in a point of trisection. (EXERCISES, p. 3, No. 5.) Also the straight line joining the middle points of two sides of a triangle is parallel to the third side, and equal to half of it. (1) Let AB CD be a rhombus. In the triangles ABC, ADC, the sides AB, AC are equal to AD,...

...square of a st. line is equal to four times the square of its half. 11. The st. line which bisects two sides of a triangle, is parallel to the third side, and equal to one half of it. 12. If two sides of a triangle be given, its area will be greatest when they contain...

...Therefore DQ=D R. Consequently PR, which is equal to P D+DR, is equal to P D+D Q. Therefore EC=P D+D Q. 2. The line joining the middle points of two sides of a triangle is equal to half the third side, and is parallel to it. Let ABC be the triangle, D and E the middle points...

...1, 2, 3, 4, etc. (I. App., schol. 2), the corresponding areas are 1, 4, 9, 16, etc. Conversely. — The line joining the middle points of two sides of...parallel to the third side, and equal to one-half of it. In the triangle ABC, let AB, AC be bisected in D and E. The line joining these points is parallel to...

...BC in 0. Join PO and draw AQ- parallel to it. Then PQ shall bisect the triangle.] 53. The straight line joining the middle points of two sides of a triangle is parallel to the third side and equal to half of it. 54. The straight lines joining the middle points of the four sides of any quadrilateral...

...corresponding height are given. EXERCISES ON BOOK III. 92. The straight line which joins the centres of two sides of a triangle is parallel to the third side, and equal to half that side. 93. The straight lines which join the centres of the consecutive sides of a quadrilateral...

...parallelogram (82) ; AE = EC; hence, DE bisects AC. GEOMETRY.— BOOK I. 104. Corollaries. 1. Tlie straight line joining the middle points of two sides of a triangle is parallel to the third side and equal to its half. (?) 2. The straight line drawn from the middle point of one of the non-parallel sides of...

...triangle parallel to the base passes through the middle point of the other side. COR. 2. The straight line joining the middle points of two sides of a triangle is parallel to the base. [Cor. i. and Rule of Identity.] SECTION 4. PROBLEMS. PROB. i. To bisect a given angle. PROB....