Example 15 - Chapter 3 Class 11 Trigonometric Functions
Last updated at April 16, 2024 by Teachoo
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Chapter 3 Class 11 Trigonometric Functions
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Transcript
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 𝒄𝒐𝒔𝛑/𝟒 𝒄𝒐𝒔𝒙 = 2 × 1/√2 cos𝑥 = √𝟐 𝒄𝒐𝒔𝒙 = R.H.S.
