Example 15 - Chapter 3 Class 11 Trigonometric Functions

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Example 15 Prove that cos (π/4+𝑥) + cos (π/4−𝑥) = √2 cos 𝑥 Solving L.H.S. cos (π/4+𝑥) + cos⁡(π/4−𝑥) = 2 cos ((π/4 " + " 𝑥 + π/4 " − " 𝑥 )/2) cos ((π/4 " + " 𝑥 − (π/4 " − " 𝑥) )/2) = 𝟐 𝒄𝒐𝒔⁡𝛑/𝟒 𝒄𝒐𝒔⁡𝒙 = 2 × 1/√2 cos⁡𝑥 = √𝟐 𝒄𝒐𝒔⁡𝒙 = R.H.S.

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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