#3sec^2thetatan^2theta+1=sec^6theta-tan^6theta#
Right Side#=sec^6theta-tan^6theta#
#=(sec^2theta)^3-(tan^2theta)^3#->use difference of two cubes formula
#=(sec^2theta-tan^2theta)
(sec^4theta+sec^2thetatan^2theta+tan^4theta)#
#=1 *(sec^4theta+sec^2thetatan^2theta+tan^4theta)#
#=sec^4theta+sec^2thetatan^2theta+tan^4theta#
#=sec^2theta sec^2 theta+sec^2thetatan^2theta+tan^2theta tan^2 theta#
#=sec^2theta(tan^2theta+1) +sec^2thetatan^2theta+tan^2theta(sec^2theta-1)#
#=sec^2thetatan^2theta+sec^2theta+sec^2thetatan^2theta+sec^2thetatan^2theta-tan^2theta#
#=sec^2thetatan^2theta+sec^2thetatan^2theta+sec^2thetatan^2theta+sec^2theta-tan^2theta#
#=3sec^2thetatan^2theta +1#
#=# Left Side