396 PRACTICAL MATHEMATICS 



B 1 = -{l-804-3-98cos30 + 4-5cos60 -0-80cos60 





= i{l-80 + 4-16 cos 30 + 3-7 cos 60} 

 6 



Bj-1-21 



To get A 2 and B 2 (Fig. 132). 



3-58 S^ >S* 8 



3-ZO 



FIG. 132. 

 A 2 = i{0-48 sin 60 + 3-58 sin 60} 



= | (4-06 sin 60} 

 = 0-59 

 B 2 = i{0-48 cos 60 - 3-58 cos 60 - 3-20} 



= i{- 3-10 cos 60 -3-20} 

 6 



= -0-79 

 To get A 3 and B 3 (Fig. 133). 



L? 



6 



A 3 = ~ = 0-2 



B 3 = -= -0-32 



Hence y = 3-29 + 1-21 cos - 0-79 cos 20 - 0-32 cos 30 

 + 1-51 sin + 0-59 sin 20 + 0-20 sin 30 



