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Ex 3.3, 8 Prove that cos⁑〖 (Ο€ + π‘₯) cos⁑〖(βˆ’ π‘₯)γ€— γ€—/(sin⁑〖 (Ο€ βˆ’ π‘₯)γ€— cos⁑〖"(" Ο€/2 " + " π‘₯")" γ€— ) = cot2 π‘₯ Solving L.H.S. 𝒄𝒐𝒔⁑〖(𝝅 + 𝒙) 〖𝒄𝒐𝒔 〗⁑〖(βˆ’π’™)γ€— γ€—/(π’”π’Šπ’β‘(𝝅 βˆ’ 𝒙) 𝒄𝒐𝒔⁑〖"(" 𝝅/𝟐 " + " 𝒙")" γ€— ) Putting Ο€ = 180Β° = π‘π‘œπ‘ β‘γ€–(180Β° + π‘₯) γ€–π‘π‘œπ‘  〗⁑〖(βˆ’π‘₯)γ€— γ€—/(𝑠𝑖𝑛⁑(180Β° βˆ’ π‘₯) π‘π‘œπ‘ β‘γ€–"(" 90Β° "+ " π‘₯")" γ€— ) Using cos (180Β° + x) = –cos x cos (βˆ’x) = cos x sin (180Β° – x) = sin x & cos(90Β° + x) = –sin x = (βˆ’π’„π’π’”β‘γ€–π’™ Γ— 𝒄𝒐𝒔⁑𝒙 γ€—)/((π’”π’Šπ’β‘γ€–π’™) Γ—γ€–(βˆ’π’”π’Šπ’γ€—β‘π’™) γ€— ) = (βˆ’π‘π‘œπ‘ 2π‘₯)/(βˆ’π‘ π‘–π‘›2π‘₯) = cot2x = R.H.S. Hence proved

  1. Chapter 3 Class 11 Trigonometric Functions
  2. Serial order wise

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo