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Question 7 Find the equation of tangent to the curve given by x = a sin3 t , y = b cos3 t at a point where t = ๐œ‹/2 . The curve is given as x = a sin3t , y = b cos3t Slope of the tangent = ๐‘‘๐‘ฆ/๐‘‘๐‘ฅ Here, ๐’…๐’š/๐’…๐’™ = (๐’…๐’š/๐’…๐’•)/(๐’…๐’™/๐’…๐’•) ๐’…๐’š/๐’…๐’• = (๐‘‘(๐‘ cos^3โกใ€–๐‘ก)ใ€—)/๐‘‘๐‘ก = โˆ’3b cos^2 ๐‘ก sinโก๐‘ก ๐’…๐’™/๐’…๐’• = (๐‘‘(๐‘Ž sin^3โกใ€–๐‘ก)ใ€—)/๐‘‘๐‘ก = 3a sin^2โก๐‘ก cosโก๐‘ก Hence, ๐‘‘๐‘ฆ/๐‘‘๐‘ฅ = (dy/dt)/(๐‘‘๐‘ฅ/dt) = (โˆ’3๐‘๐‘๐‘œ๐‘ ^2 ๐‘ก sinโก๐‘ก)/(3๐‘Ž sin^2โกใ€–๐‘ก cosโก๐‘ก ใ€— ) = (โˆ’๐’ƒ ๐’„๐’๐’”โก๐’•)/(๐’‚ ๐’”๐’Š๐’โก๐’• ) Now, Slope of the tangent at "t = " ๐œ‹/2 is ๐’…๐’š/๐’…๐’™ = (โˆ’๐‘ ใ€–cos ใ€—โกใ€–๐œ‹/2ใ€—)/(๐‘Ž ใ€–sin ใ€—โกใ€–๐œ‹/2ใ€— ) = (โˆ’๐‘(0))/(๐‘Ž(1)) = 0 To find Equation of tangent, we need to find point (x, y) Putting t = ๐œ‹/2 in equation of x and y ๐‘ฅ = ๐‘Ž sin3 (๐œ‹/2) ๐’™=๐’‚ ๐‘ฆ = b cos3 (๐œ‹/2) y = 0 Hence, point is (a, 0) Now, Equation of tangent at point (๐‘Ž, 0) and with slope 0 is y โˆ’ 0 = 0 (x โˆ’ ๐‘Ž) y = 0

  1. Chapter 6 Class 12 Application of Derivatives
  2. Serial order wise

About the Author

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