If and prove that
Proof:
We know,
sin2 α + cos2 α = 1
⇒ cos2 α = 1 – sin2 α
Similarly,
sin2 β + cos2 β = 1
⇒ sin2 β = 1 – cos2 β
Identity used:
cos (α – β) = cos α cos β + sin α sin β
Hence Proved