A Geometry for Beginners

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Ginn & Heath, 1880 - Geometry - 314 pages
 

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Page 117 - Two triangles are congruent if two sides and the included angle of one are equal respectively to two sides and the included angle of the other.
Page 140 - The area of a rectangle is equal to the product of its base and altitude. Given R a rectangle with base b and altitude a. To prove R = a X b. Proof. Let U be the unit of surface. .R axb U' Then 1x1 But - is the area of R.
Page 141 - The area of a parallelogram is equal to the product of its base and its height: A = bx h.
Page 92 - Hence the arc drawn from the vertex of an isosceles spherical triangle, to the middle of the base, is perpendicular to the base, and bisects the vertical angle.
Page 269 - The altitude of a pyramid is the length of the perpendicular from the vertex of the pyramid to the plane of the base.
Page 124 - A regular polygon of three sides is called an equilateral triangle ; oifour sides, a square ; of five sides, a pentagon ; of six sides, a hexagon ; of seven sides, a heptagon ; of eight sides, an octagon ; of nine sides, a nonagon ; of ten sides, a decagon ; of twelve sides, a dodecagon.
Page 125 - Theorem. — The sum of all the angles of a polygon is equal to twice as many right angles as the polygon has sides, less two.
Page 180 - If in a right triangle a perpendicular is drawn from the vertex of the right angle to the hypotenuse : I.
Page 79 - If two angles of one triangle are equal respectively to two angles of another triangle, the third angles are equal.

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