Question

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°?

Answer 1

The answer is A

Answer 2

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°