Simplify cos(40 degrees )^2-sin(40 degrees )^2

$\cos^{2} (40 °) - \sin^{2} (40 °)$

Step 1

Apply the cosine double-angle identity.

$\cos (2 \cdot 40 °)$

Step 2

Multiply $2$ by $40 °$ .

$\cos (80)$

Step 3

The result can be shown in multiple forms.

Exact Form:

$\cos (80)$

Decimal Form:

$0.17364817 \dots$