MATHEMATICS 

 PRISM OR PARALLELOPIPED 



55 



For prisms with- regular polygon as 

 bases, p = length of one side X number of sides. 



To obtain area of base, if it is a polygon, divide it into tri- 

 angles, and find sum of partial areas. 



FRUSTUM OF PRISM 



If a section perpendicular to the edges is a tri- 

 angle, square, parallelogram, or regular polygon, 



sum of lengths of edges 

 number of edges 



X area of right section. 



REGULAR POLYGONS 



Divide the polygon into equal triangles and find the sum of 

 the partial areas. Otherwise, square the length of one side 

 and multiply by proper number from the following table: 



IRREGULAR AREAS 



Divide the area into trapezoids, triangles, parts 

 of circles, etc., and find the sum of the partial areas. 



If the figure is very irregular, the approximate 

 area may be found as follows: Divide the figure 

 into trapezoids by equidistant parallel lines b, c, d, 

 etc. The lengths of these lines being measured, 

 then, calling a the first and n the last length, and 

 y the width of strips, 



area = y(^2 +b + c + etc. + m) 



