Example 9 - Chapter 8 Class 10 Introduction to Trignometry

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Example 9 Express the ratios cos A, tan A and sec A in terms of sin A. cos A Since, cos2 A + sin2 A = 1 cos2 A = 1 โ€“ sin2 A cos A = ยฑโˆš(๐Ÿ โˆ’๐’”๐’Š๐’๐Ÿ ๐‘จ) Here, A is acute (i.e. less than 90ยฐ) & cos A is positive when A is acute So, cos A = โˆš(๐Ÿ โˆ’๐’”๐’Š๐’๐Ÿ ๐‘จ) sec A sec A = 1/cosโกใ€– ๐ดใ€— sec A = ๐Ÿ/โˆš(๐Ÿ โˆ’๐’”๐’Š๐’๐Ÿ ๐‘จ) tan A We know that tan A = ๐‘ ๐‘–๐‘›โกใ€– ๐ดใ€—/๐‘๐‘œ๐‘ โกใ€– ๐ดใ€— Putting value of cos A tan A = ๐’”๐’Š๐’โกใ€– ๐‘จใ€—/โˆš(๐Ÿ โˆ’ ๐’”๐’Š๐’๐Ÿ ๐‘จ)

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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