Which expression is equal to sin 75°? sin 135° cos 60° - cos 135° sin 60° cos 135° cos 60° + sin 135° sin 60° sin 135° cos 60° + cos 135° sin 60° cos 135° cos 60° - cos 135° cos 60°?

These are the sum/difference formulas in trigonometry. The first formula is in accordance with sin (α - β) = sinα * cosβ - cosα * sinβ. If we combine the first one with this formula, we'll obtain sin 135° cos 60° - cos 135° sin 60° = sin (135-60) = sin75 °