Use identities to fill in each blank with the appropriate trigonometric function name.
____ 72° = cot 18°

Find the exact value of each expression. See Example 1.

[tan 80° - tan(-55°)]/[ 1 + tan 80° tan(-55°)]

Use the given information to find sin(x + y).

cos x = 2/9, sin y = - 1, x in quadrant IV, y in quadrant III

Use identities to fill in each blank with the appropriate trigonometric function name.

sin 2π/3 = _____ (- π/6)

Find the exact value of each expression. See Example 1.

[tan 5π/12 + tan π/4]/[1 - tan 5π/12 tan π/4]

Write each function as an expression involving functions of θ or x alone. See Example 2.

cos(θ - 30°)

Use identities to fill in each blank with the appropriate trigonometric function name.

tan 24° = 1/ _____ 66°

Write each function as an expression involving functions of θ or x alone. See Example 2.

cos(45° - θ)

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

tan θ = cot(45° + 2θ)