                        7  9    7  10                                   Ε     P                 c    m          
 ＝    ×                                    8—4 
  P＝mc                                                                          8—5 
      7—8                   
                      
 ＝                                                   8—6 
                      
             c
  P＝                                                                       8—7 
             E
          
                                             
   ×    ＝                           8—8 
                                              
                     c
       mc＝                                                                8—9 
                     E
    c 
          c²
m ＝                                                                           8—10 
      E
                        
  ＝                                           8—11 
                            (    
                     
                                   E —                                    m      mc²                                mº    mºc²                                   mºc²    

                                                                                                                                
    19                                                                          c²            