# Use the sum/difference formula to find the exact value of the following.

**Question description**

These are the questions please give the answer with the steps how did you get it :

1. Use the sum/difference formula to find the exact value of the following.

a) cos 11π/12

b) tan 165◦

2. Evaluate cos(θ − φ), where cos θ = 7/25 with θ in Quadrant IV, and tan φ = −√3 with φ in Quadrant II.

3. Given that tanθ = 1/−3, and cosθ > 0, find sin2θ, cos2θ, and tan2θ.

4. Use the appropriate Half-Angle Formula to find the exact value of each expression.

a) sin 15◦

b) sin 157.5◦

c) cos 11π/8

5. Find the general solution of cos θ = − 1/2

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