Evaluate:
sin 15° cos 15° - cos 75° sin 75°
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= sin (90° - 75°) cos (90° - 75°) - cos (90° - 15°) sin 75°
= cos 75° sin 75° - cos 75° sin 75°
= 0
Hence, sin 15° cos 15° - cos 75° sin 75° = 0.
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Evaluate :
sin (90° - A) sin A - cos (90° - A) cos A