234 



PRACTICAL MATHEMATICS 



126. The Parallelogram and the Triangle. 



(1) Let a be the base and h the height of a parallelogram, and 

 let OX be an axis drawn parallel to the base through the centroid. 



/ 



FIG. 64, 



Consider an elementary strip of breadth 8?/ drawn parallel to 

 the axis OX and at a distance y from it. 

 The moment of inertia of this strip about OX = ay 2 &/. 

 The moment of inertia of the parallelogram about OX 



ay 2 dy. 



l ox 



A 



fa 

 - a I y 2 dy 



J h 



12 



(2) Let a be the base and h the height of a triangle. 



C 



a, 



FIG. 65. 



