6

cos 15° cos 35° cosec 55° cos 60° cosec 75° =1/2

6

cos 1° cos 2° cos 3° ... cos 180° = 0

7

Prove that:

sin (70°+θ) — cos (20° — θ) = 0

7

tan (55° — θ) — cot (35° + θ) = θ