### Sum and difference identities

Find the coordinates of P(π/12) x = (1+√3)/(2√2) To find the y-coordinate you use the identity: sin(α - β) = (sinα)(cosβ) (cosα)(sinβ) Why do we use this identity? eg, why don't we use sin(α + β) = (sinα)(cosβ) + (cosα)(sinβ) ??