Find the value of:
`cos150^(@)`

Explanation

To find the value of \( \cos 150^\circ \), we can follow these steps:

### Step 1: Identify the angle in terms of known angles
We can express \( 150^\circ \) as \( 180^\circ - 30^\circ \). This will help us use the cosine subtraction identity.

### Step 2: Use the cosine identity
Using the cosine identity for angles in the second quadrant:
\[
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