ANALY1K r;/;o.V /;//;! [Cn. V 



Since </>=0| 6* 



tan * - *"*.-tog. ( Art . 

 1 + tan 0| tan O t 



=i 



If the angle were measured from HIM- ( 1 ) t<> line ( *J > it 

 would be the negative, or else tin- siipplnm-ut. ..I $; in 

 cither case its tangent would be the negative of that given 

 by formula [14]. 



If the equations of the lines had been given in the form : 



+ ,y + (7, = 0, . . (3) 



and Ap -f B$ -f C 2 = 0, . . . (4) 



thru wi l = ', TH? = ?, and formula [14] becomes 



' 





A^Bi - A,B, 



EXERCISES 



Find the tangent of the angle from the first line to the second in each 

 of the following cases, and draw the figures : 



2. 5*+ 12y + l=0, 



3. -Jz = 3 + 9 6 



5. zcosa + y sin a = p, ? + ^ = l. 



a b 



62. Condition that two lines are parallel or perpendicular. 

 1- r>iii formula [14] can be seen ;it once the relations that 



