#LHS=sin^2alpha+sin^2beta-sin^2gamma#
#=1/2(1-cos2alpha)+1/2(1-cos2beta)-1/2(1-cos2gamma)#
#=1/2(1+cos2gamma-(cos2alpha+cos2beta))#
#=1/2(2cos^2gamma-(2cos(alpha+beta)cos(alpha-beta))#
#=cos^2gamma-cos(pi+gamma)cos(alpha-beta)#
#=cosgamma*cosgamma+cosgammacos(alpha-beta)#
#=cosgamma*cosgamma+cosgammacos(alpha-beta)#
#=cosgamma(cos(alpha-beta)+cos(alpha+beta-pi))#
#=cosgamma(cos(alpha-beta)-cos(alpha+beta))#
#=cosgamma*2sinalphasinbeta#