Double Angle Identities

6. Trigonometric Identities and More Equations / Double Angle Identities / Problem 4

Determine the exact value of the following expression by writing it as the cosine of a double angle.
cos² 112.5° - sin² 112.5°

(√2)/2

-1/2

-(√3)/2

-(√2)/2

Determine the exact value of the following expression by writing it as the cosine of a double angle.cos² 112.5° - sin² 112.5°