TRIGONOMETRY gl 



Given Sought Formula 



7 , tan c sin d> 



o tan b = -: 



sin (a + 



sn - tan 



, ft, 7 e cot }6 = *** + cos 



sn 7 

 0, &, c tan 2 Je = tan J5 tan }(j - a) tan J( 5 - b) 



tan }(s - c). 

 e )T 5 5-^. 



FINITE SERIES OF CIRCULAR FUNCTIONS 



3.60 If the sum, / (r), of the finite or infinite series: 



/ W = a + ai r + a 2 r 2 + 



is known, the sums of the series: 



Si = a cos x + 0i r cos (x + y) + a 2 r 2 cos (x + 2y) + . . . . 

 6*2 = GO sin x + ai r sin (x + y) + a? r 2 sin (#+23;) + .... 



are: 



3.61 Special Finite Series. 



. nx . n+i 



sin sin x 



2 2 

 i. 7 ,smkx = - 



sin - 

 2 



nx . n + i 



cos sm x 



,22 

 2. / j cos J?oe = 



. x 

 k=o sin - 



2 



