Prove that Sin θ Sin( 90° - θ) - Cos θ Cos( 90° - θ) = 0

Prove that sin θ sin( 90° - θ) - cos θ cos( 90° - θ) = 0

Sum

LHS = sin θ sin( 90° - θ) - cos θ cos( 90° - θ)

= sin θ . cos θ - cos θ . sin θ

= 0
= RHS
Hence proved.

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