To find the reference angle for \(\cos(225^\circ)\), follow these steps:

1. First, note that \(225^\circ\) is in the third quadrant, where cosine is negative.
2. The reference angle is the smallest angle formed between the terminal side of the angle and the x-axis.
3. In the third quadrant, the reference angle is found by subtracting \(180^\circ\) from the given angle:
   \[
   \text{Reference angle} = 225^\circ - 180^\circ = 45^\circ
   \]

Thus, the reference angle for \(225^\circ\) is \(45^\circ\).

Would you like to go over further details or have any questions?

Here are 5 related questions:
1. What is the sine of \(225^\circ\)?
2. How do you determine the reference angle for an angle in the fourth quadrant?
3. What is the cosine of a reference angle of \(30^\circ\)?
4. How does cosine behave in the third quadrant?
5. What is the general formula for finding a reference angle in any quadrant?

**Tip:** The reference angle is always between \(0^\circ\) and \(90^\circ\), regardless of which quadrant the original angle lies in.

Learn how to find the reference angle for cos 225 degrees using simple trigonometric rules. Understand how angles in the third quadrant behave and calculate the reference angle with clear steps. This guide covers key trigonometric concepts, suitable for students in Grades 9-11.

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