217-219. J I' L.I N>. - \M> KS HI 



a constant factor, m < 208, eqs. [6]; also 



m (7 - 

 [I]- 00* + OOS*0 + OOS*7- 



- 1, and m- 



Then cta = 



x t /; r- 

 Equation (1) written in th.- normal form is 



;f 



[-1] 



\ .1- + IP + < - 



therefore, to reduce equation (1) to the normal form, it is neo- 

 essary only to trantpotc the constant term to the ueond m^m- 

 ber of the equation, and then divide both member* by the $quar* 

 root of the turn o/ e he iquare* of the coefficient* of the variable 

 term*. The sign of the radical in determined by the fact 

 17) that p U taken positive ; hence, the rig* of the 

 radical i* the oppoeite of the *iyn of the eon*tant term. 



219. The angle between two planes. Parallel and perpen- 

 dicular planes. The angles formed by two intersecting 

 planes are the same as the angles formed by two straight 

 linos perpendicular to them respectively; i.<,, are the 



