1+ctqa*ctqb*cos(a+b)/cosa*cosb=1+cosa/sina*cosb/sinb*cos(a+b)/cosa*cosb=1+cos(a+b)/sina*sinb=1+cosa*cosb-sina*sinb/sina*sinb=sina*sinb+cosa*cosb-sina*sinb/sina*sinb=sina*sinb(1+cosa*cosb)/sina*sinb=1+cosa*cosb
1+ctqa*ctqb*cos(a+b)/cosa*cosb=1+cosa/sina*cosb/sinb*cos(a+b)/cosa*cosb=1+cos(a+b)/sina*sinb=1+cosa*cosb-sina*sinb/sina*sinb=sina*sinb+cosa*cosb-sina*sinb/sina*sinb=sina*sinb(1+cosa*cosb)/sina*sinb=1+cosa*cosb