This question is from trigonometry topic- trigonometric ratios on complementary angles in which we have been asked to prove that cos15° cos35° cosec55° cos60° cosec75° = 2
RS Aggarwal, Class 10, chapter 12, question no 6(iii)
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Consider L.H.S. = cos 15° cos 35° cosec 55° cos 60° cosec 75°
= cos 15° cosec 75° cos 35° cosec 55° cos 60°
= cos 15° cosec (90-15)° cos 35° cosec (90-35)° cos 60°
= (cos 15° sec 15°) × (cos 35° sec 35°) × cos 60°
= (1) × (1) × (1/2)
= 1/2 = R.H.S.
Hence, proved.