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°)

In Exercises 35–38, find the exact value of the following under the given conditions: b. cos(α﹣β)

sin α = 3/5, 0 < α < 𝝅/2, and sin β = 12/13, 𝝅/2 < β < 𝝅.

Find the exact value of the expression.

$\(\cos\)105\(\degree\)$

Find the exact value of the expression.

$\(\sin\)15\(\degree\)$

Find the exact value of the expression.

$\(\cos\)80\(\degree\[\cos\)20\(\degree\)+\(\sin\)80\(\degree\]\sin\)20\(\degree\)$

Expand the expression using the sum & difference identities and simplify.

$\(\sin\[\left\)(-\(\theta\)-\(\frac{\pi}{2}\]\right\))$

Find the exact value of the expression.

$\(\tan\)105\(\degree\)$

Expand the expression using the sum & difference identities and simplify.

$\(\tan\[\left\)(-\(\theta\)-\(\frac{\pi}{2}\]\right\))$