Question

The value of cos 9${}^{\circ }$ - sin 9${}^{\circ }$ is

• A. $-\frac{\sqrt{5-\sqrt{5}}}{2}$
• B. $\frac{5+\sqrt{5}}{4}$
• C. $\frac{1}{2}\sqrt{5-\sqrt{5}}$
• D. none of these.

Answer 1

Answer: (C)

Correct answer is (c) $\frac{1}{2}\sqrt{5-\sqrt{5}}$