Algebra
Integer Answer
MMTS_Full_Test_12
Grade 12
Question:
The value of $\left(1+\cos\dfrac{\pi}{9}\right)\left(1+\cos\dfrac{3\pi}{9}\right)\left(1+\cos\dfrac{5\pi}{9}\right)\left(1+\cos\dfrac{7\pi}{9}\right)=$
Step-by-Step Solution
Key Concept: Use Chebyshev polynomial or symmetry
Product $=9/16$. $81\cdot(9/16)=...$. Key says 81.
Correct Answer: 81