If 2 sin 2 ⁡β – cos 2 ⁡β  = 2, then β is

(a) 0ᵒ   (b) 90ᵒ   (c) 45ᵒ   (d) 30ᵒ

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  1. Class 10
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Transcript

Question 7 If 2 sin^2⁡𝛽 – cos^2⁡𝛽 = 2, then β is (a) 0ᵒ (b) 90ᵒ (c) 45ᵒ (d) 30ᵒ Given 2 sin^2⁡𝛽 – cos^2⁡𝛽 = 2 – cos^2⁡𝛽 = 2 − 2 sin^2⁡𝛽 – 〖𝒄𝒐𝒔〗^𝟐⁡𝜷 = 2(1 − 〖𝒔𝒊𝒏〗^𝟐⁡𝜷) – cos^2⁡𝛽 = 2 cos^2⁡𝛽 0 = 2 cos^2⁡𝛽 "+ " cos^2⁡𝛽 0 = 3 cos^2⁡𝛽 3 cos^2⁡𝛽 = 0 cos^2⁡𝛽 = 0 𝒄𝒐𝒔⁡𝜷 = 0 This is possible if 𝛽 = 90° So, the correct answer is (b)

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.