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Ex 8.4, 4 - Chapter 8 Class 10 Introduction to Trignometry - Part 2

Ex 8.4, 4 - Chapter 8 Class 10 Introduction to Trignometry - Part 3

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Ex 8.3, 4 Choose the correct option. Justify your choice. (ii) (1 + tan θ + sec θ) (1 + cot θ – cosec θ) (A) 0 (B) 1 (C) 2 (D) –1 (1 + tan θ + sec θ) (1 + cot θ – cosec θ) Writing in terms of sin θ & cos θ = (1+" " sin⁡𝜃/cos⁡𝜃 " + " 1/cos⁡𝜃 " " ) (1+" " cos⁡𝜃/sin⁡𝜃 " − " 1/sin⁡𝜃 " " ) = ((cos⁡𝜃 +sin⁡𝜃 + 1))/cos⁡𝜃 × ((sin⁡𝜃 +cos⁡𝜃 − 1))/sin⁡𝜃 = (({cos⁡𝜃 +sin⁡𝜃 } + 1) ({sin⁡𝜃 +cos⁡𝜃 }− 1))/(cos⁡𝜃 sin⁡𝜃 ) = ( (cos⁡𝜃 +sin⁡𝜃 )2 −12)/(cos⁡𝜃 sin⁡𝜃 ) = (𝑐𝑜𝑠2 𝜃 + 𝑠𝑖𝑛2 𝜃 +2 cos⁡𝜃 sin⁡𝜃 − 1)/(cos⁡𝜃 sin⁡𝜃 ) = (1 + 2 cos⁡𝜃 sin⁡𝜃 − 1)/(cos⁡𝜃 sin⁡𝜃 ) = (2 cos⁡𝜃 sin⁡𝜃)/(cos⁡𝜃 sin⁡𝜃 ) = 2 Answer = 2 Hence, option (B) is correct.

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.