## If cos 9α = sin α and 9α < 90° , then the value of tan 5α is

## (A) 1/√3 (B) √3 (C) 1 (D) 0

Last updated at Aug. 19, 2021 by Teachoo

Transcript

Question 10 If cos 9α = sin α and 9α < 90° , then the value of tan 5α is (A) 1/√3 (B) √3 (C) 1 (D) 0 Given cos 9α = sin α cos 9α = cos (90° − α) Comparing angles 9α = 90° − α 9α + α = 90° 10α = 90° α = (90° )/(10° ) α = 9° Now, tan 5α = tan (5 × 9°) = tan 45° = 1 So, the correct answer is (C)

NCERT Exemplar - MCQ

Chapter 8 Class 10 Introduction to Trignometry (Term 1)

Serial order wise

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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.