NCERT Solutions for Class 10 Maths Chapter 8
Important NCERT Questions
Introduction Trigonometry
NCERT Books for Session 2022-2023
CBSE Board and UP Board Others state Board
EXERCISE 8.3
Page No:189
Questions No:5
If sec 4A = cosec (A – 20°), where 4A is an acute angle, find the value of A.
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Given that: sec 4A = cosec(A – 20°)
⇒ cosec(90° – 4A) = cosec(A – 20°) [∵ cosec(90°- θ) = sec θ]
⇒ 90°-4A = A – 20°
⇒ 90°+20° = 5A ⇒ 5A = 110° A = 22°
Hence, A = 22°
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