F I G 



TABLE, 



Of ihe focal length of the convex or magnifying glasses, commonly requir- 

 ed at various ages. ( Kitchiner.) 



The following is an easy method of finding 1 which of two concave or 

 convex glasses magnifies most. Hold one in .each hand about one foot 

 from your eye, and about five feet from a window frame, and the lens, 

 through which the panes of glass appear least> magnifies most. This is 

 the readiest way of ascertaining their comparative power. 



F 



FIGURE of the sines, $c. 



Figure of the sines, cosines, tangents, secants ; to find the area of, 



4. Figure of the sines. 



Let 6 arc or abscissa, then area =- r X ver. siu. 0, 



When 6 is a quadrant, area - r*. 



2. Figure <of the cosines. 

 Area = r X sin. 9. 



When 6 is a, quadrant, area r*. 



3. Figure of the tangents. 



Area - r X h. I. 



When is a quadrant, area is infinite. 



Cor. The solid, generated by the revolution ef the figure of the tan- 

 gents about its base, is equal to a cylinder, the base of which is the cir- 

 cle, and height =. excess of tang. & above 9. 

 H3 G2 



