Find the values of the following trigonometric ratios :

Options

A. `cos225^@`
B. `sin 690^@`
C. `tan(-390^@)`
D. `sec 855^@`

Explanation

To find the values of the given trigonometric ratios, we will analyze each one step by step.

### Step 1: Calculate cos(225°)
1. **Identify the angle**: 225° can be expressed as 180° + 45°.
2. **Determine the quadrant**: Since 225° is in the third quadrant, the cosine function is negative in this quadrant.
3. **Use the cosine identity**:
\[
\cos(225°) = \cos(180° + 45°) = -\cos(45°)
...