## Marks' First Lessons in Geometry: Objectively Presented |

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acute angle adjacent angles Blue adjacent angles Green adjacent angles Yellow angle b a c angle b c d angles are equal angles whose vertices AXIOM called circle circumference curved line DEMONSTRATION DEVELOPMENT LESSON Diagram equal sides equilateral triangle exterior and interior Geometry given to Fig greater half the arc inches long included angle interior alternate angles interior angles Red interior opposite angles isosceles triangle line C D line e ƒ means of Fig measured by half obtuse angle opposite exterior parallel parallelogram particular name perpendicular polygon Produce the side PROPOSITION Prove the interior quadrilateral radii radius Read four rectangle rhomb rhomboid right angles right-angled triangle Sanders scalene triangle secant separately equal side A B square inches straight lines a b tangent TEST LESSON THEOREM thing three angles three names three squares trapezium trapezoid triangle a b c units long vertex wish to prove

### Popular passages

Page 74 - PERIPHERY of a circle is its entire bounding line ; or it is a curved line, all points of which are equally distant from a point within called the center.

Page 25 - ACE is a right angle. An Acute Angle is one which is less than a right angle ; as the angle BCD.

Page 124 - America, but know that we are alive, that two and two make four, and that the sum of any two sides of a triangle is greater than the third side.

Page 148 - If two triangles have two sides and the included angle of the one, equal to two sides and the included angle of the other, each to each, the two triangles will be equal in all their parts." Axiom 1. "Things which are equal to the same thing, are equal to each other.

Page 24 - An ACUTE ANGLE is one which is less than a right angle ; as the angle DEF.

Page 147 - If two triangles have the three sides of the one equal to the three sides of the other, each to each, the triangles are congruent.

Page 3 - The elements of Geometry are much easier to learn, and are of more value when learned, than advanced Arithmetic ; and, if a boy is to leave school with merely a grammar-school education, he would be better prepared for the active duties of life with a little Arithmetic and some Geometry, than with more Arithmetic and no Geometry.

Page 138 - If two triangles have two angles and the included side of the one, equal to two angles and the included side of the other, each to each, the two triangles will be equal.