1) T3−t5T1=T5−T7T3
LHS sin3θ+cos3θ−sin5θ−cos5θsin θ+cos θ
=sin3θ+sin5θ−cos5θsin θ+cos θ
=sin3θ(1−sin2θ)+cos3θ(1−cos2θ)sin θ+cos θ
=sin3θ.cos3θ+cos3θ.sin2θsin θ+cos θ
=sin2θ.cos2θ
RHS sin5θ=sin7sin θ+cos5θ−cos7θsin3θ+cos3θ
=sin5θ(1−sin2θ)+cos5θ(1−cos θ)sin3θ+cos3θ
=sin5θ.cos2θ+cos5θ.sin2θ(sin3θ+cos3θ) (Now take out common terms)
=sin2θ.cos2θ =LHS proved