34 



MA I II EM A TICS 



Any triangle inscribed in a semicircle is a right triangle, and 



c:b = a:h 

 fc i\. J 



ab ce 

 c a 



For any triangle, 



2b 



A1 so. A = 



in which s=$(a+b + c). 



- a) (s - b) (s - c) 



RECTANGLE AND PARALLELOGRAM 



- 7 A = ab 



TRAPEZOID 



TRAPEZIUM 



Divide the figure into two triangles and a trapezoid; then, 



or, A = \[bh' 



Or, divide into two triangles by drawing a 

 diagonal. Considering the diagonal as the base 

 of both triangles, call its length /, and call 

 the altitudes of the triangles hi and fo; then, 



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: 



