**2.**the continuous line forming the boundary of a closed geometric figure.**7.**the trigonometric function that is equal to the ratio of the side opposite a given angle (in a right triangle) to the hypotenuse.**8.**a triangle) having sides unequal in length.**10.**each angular point of a polygon, polyhedron, or other figure.**13.**a triangle) having two sides of equal length.**15.**a plane figure with 9 straight sides and angles.**19.**the quality of being made up of exactly similar parts facing each other or around an axis.**20.**a plane figure with four equal straight sides and four right angles.**21.**the space (usually measured in degrees) between two intersecting lines or surfaces at or close to the point where they meet.**23.**Lying next to each other.**26.**The part of a circle made by a line and a connecting arc.**27.**a plane figure with at least three straight sides and angles.

**1.**A straight line at an angle of 90° to a given line, plane, or surface.**3.**Curved inwards.**4.**unproven statement which is supported by all the available data and by many weaker results.**5.**a plane figure with seven straight sides and angles.**6.**The part of a conditional statement after then.**9.**a plane figure with twelve sides.**11.**a parallelogram with opposite equal acute angles, opposite equal obtuse angles, and four equal sides.**12.**A line with a start point but no end point.**14.**the trigonometric function that is equal to the ratio of the side adjacent to an acute angle (in a right-angled triangle) to the hypotenuse.**16.**a plane figure with eight straight sides and eight angles.**17.**a plane figure with three straight sides and three angles.**18.**reasoned, logical explanations that use definitions, axioms, postulates, and previously proved theorems to arrive at a conclusion about a geometric statement.**22.**A long thin mark made by a pen, pencil, etc.**24.**A plane figure with ten straight sides and angles.**25.**A result that has been proved to be true.