### Home > PC > Chapter 11 > Lesson 11.2.1 > Problem 11-75

11-75.

Use the Angle Sum and Difference Identities.

This expression is equivalent to −[cos(4*y*)cos(4*y*) − sin(4*y*)sin(4*y*)].

11-75.

Use the Angle Sum and Difference Identities.

This expression is equivalent to −[cos(4*y*)cos(4*y*) − sin(4*y*)sin(4*y*)].