6. Trigonometric Identities and More Equations

Use the identities for the cosine of a sum or difference to write each expression as a trigonometric function of θ alone.

cos(θ - 270°)

Find cos(s + t) and cos(s - t).

cos s = √2/4 and sin t = - √5/6, s and t in quadrant IV

Find one value of θ or x that satisfies each of the following.

cos x = sin (π/12)