This question is from trigonometry

Topic – Trigonometric ratios on. complementary angles

We have to prove that sec70°sin20° + cos20°cosec70° = 2 without using trigonometric tables

RS Aggarwal, Class 10, chapter 12, question no 2(iii).

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LHS

sec70°sin20° + cos20°cosec70°

= sec(90° – 20°) sin20° + cos20° cosec(90° – 20°)

= cosec 20° sin20° + cos20° sec 20°

= 1 +1

= 2 = RHS