When you use angle sum and difference identities in trigonometry, it’s easy to make mistakes. Here are some common errors to watch out for:

1. Sign Mistakes: Always check your signs! The identities for sine and cosine have specific signs depending on the angles. For example, the sine of a difference is:

   $\sin(A - B) = \sin A \cos B - \cos A \sin B$

   Many people accidentally switch the signs. So, double-check!

2. Confusing Angles: Be careful not to mix up the angles in your formulas. For $\tan(A + B)$, make sure you’re using the right identity:

   $\tan(A + B) = \frac{\tan A + \tan B}{1 - \tan A \tan B}$

   Using the wrong identity can lead to mistakes.

3. Forgetting Quadrants: Remember to think about where your angle is on the unit circle! This can change the signs of your answers.

4. Simplifying Too Soon: It might be tempting to simplify your math right away. But it’s usually better to use the identities first and then simplify. This way, you can avoid errors.

By keeping these common mistakes in mind, you’ll get better at using angle sum and difference identities!