Which of the following trigonometric expressions is equal to sec6 θ ?
tan6 θ+3 tan2 θ sec2 θ+1
sec6 θ=(sec2 θ)3
=(tan2 θ+1)3……(1+tan2 θ=sec2 θ)
=tan6 θ+3 tan4 θ+3 tan2 θ+1
=tan6 θ+3 tan2 θ(tan2 θ)+3 tan2 θ+1
=tan6 θ+3 tan2 θ(sec2 θ−1)+3 tan2 θ+1
=tan6 θ+3 tan2 θ sec2 θ−3 tan2 θ+3 tan2 θ+1
=tan6 θ+3 tan2 θ sec2 θ+1