Value of Trigonometric Functions at Multiples and Submultiples of an angle – Exercise 9.3 Solutions

1. Prove that: sin² 2π/5 – sin² π/3 = (√5 – 1)/8  Watch Solution
2. Prove that: sin² 24° – sin² 6° = (√5 – 1)/8 Watch Solution
3. Prove that: sin² 42° – cos² 78° = (√5 + 1)/8 Watch Solution
4. Prove that: cos 78° cos 42° cos 36° = 1/8 Watch Solution
5. Prove that: cos π/15 cos 2π/15 cos 4π/15 cos 7π/15 = 1/16 Watch Solution
6. Prove that: cos 6° cos 42° cos 66° cos 78° = 1/16 Watch Solution
7. Prove that: sin 6° sin 42° sin 66° sin 78° = 1/16 Watch Solution
8. Prove that: cos 36° cos 42° cos 60° cos 78° = 1/16 Watch Solution
9. Prove that: sin π/5 sin 2π/5 sin 3π/5 sin 4π/5 = 5/16 Watch Solution
10. Prove that: cos π/15 cos 2π/15 cos 3π/15 cos 4π/15 cos 5π/15 cos 6π/15 cos 7π/15 = 1/128 Watch Solution