Find the Exact Value cos(pi/11)^2-sin(pi/11)^2

$\cos^{2} (\frac{π}{11}) - \sin^{2} (\frac{π}{11})$

Step 1

Apply the cosine double-angle identity.

$\cos (2 \frac{π}{11})$

Step 2

Combine $2$ and $\frac{π}{11}$ .

$\cos (\frac{2 π}{11})$

Step 3

The result can be shown in multiple forms.

Exact Form:

$\cos (\frac{2 π}{11})$

Decimal Form:

$0.84125353 \dots$