INTERNAL FORCES 



57 



to designate the sides opposite the angles. By placing the capital 

 letters so small 6 will represent the base and small a will represent 

 the altitude (height) of a triangle the student has a mnemonic 

 idea of the relations of the sides and angles. In the following 



fi cures 



a - BC (line from B to C) 

 b = AC (line from A to C) 

 c = AB (line from A to B) 



Fig. 48 Frame with Inclined Strut 

 Then in Fig. 48 6 = Vo 2 + c 2 = 8.246, 



Fig. 49 Frame with Inclined Strut and In- 

 clined Tie 



in Fig. 49 6 = c = V (a/2) 2 + (line A-a) 2 = 8.062, 



1. 



Fig. 50 Frame with Inclined Tie 



-Mr 



in Fig. 50 c 



The rule is known as the " Rule of Pythagoras " and is given 

 in every school arithmetic as follows: 



In every right-angled triangle the square on the hypothenuse is 

 equal to the sum of the squares on the other two sides. 



In Fig. 48 



cP - 8 x 3000 - 24,000 ft. Ibs. in member C. 



