### Home > PC > Chapter 8 > Lesson 8.1.1 > Problem 8-17

8-17.

Solve: sin^{4}*x* − cos^{4}*x* =

Factor.

Substitute using the Fundamental Pythagorean Identity.

Substitute using the Fundamental Pythagorean Identity.

Combine.

Divide both sides by −2.

Square root both sides. Don't forget the ±.