V 



DEFINITIONS OF MATHEMATICAL FOEMS. 



FlG - * Parallel Lines are everywhere 



equally distant ; as, A B and C D. 

 C D 



An Angle is the difference of direc- 

 tion between two lines which meet ; 

 as, A D E. The point of meeting is 

 called the vertex of the angle, and when 

 B the angle is named the letter at the 

 vertex is placed second ; as, C D E. 



A Right Angle is formed when a 

 straight line meeting another makes 

 two equal angles ; as, A D C and C D B. 



An Acute Angle is one less than a 



FIG 4 



right angle ; as, E B D, Fig. 3. 



An Obtuse Angle * is one greater 

 D than a right angle ; as, A D E, Fig. 4. 



A Surface has two dimensions length and breadth. 

 A Triangle is a figure having three sides ; as, A B C, 

 Fig. 5. 



FIG - 5 - The Altitude of a triangle is the per- 



pendicular distance of the vertex from 

 the line of the base ; as, B C is the 

 altitude of the triangle ABC, Fig. 5. 

 A Right- Angle Triangle is a triangle having aright angle ; 



* As the right angle contains 90, it follows that the acute angle contains 

 less, and the obtuse angle more, than 90. 



