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Find the magnitude of angle A, if 2 cos2 A - 3 cos A + 1 = 0 - Mathematics

Sum

Find the magnitude of angle A, if 2 cos2 A - 3 cos A + 1 = 0

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Solution

2 cos2 A –  3 cos A + 1 = 0
2 cos2 A –  cos A - 2cosA +1 = 0
cos A(2cos A –  1) –  (2 cos A – 1) = 0
( 2 cosA – 1) (cos A – 1) = 0
2 cos A –  1 = 0 aand cos A –  1 = 0
cos A = `(1)/(2)` and cos A = 1
A = 60° and A = 0°

Concept: Trigonometric Equation Problem and Solution
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APPEARS IN

Selina Concise Mathematics Class 9 ICSE
Chapter 23 Trigonometrical Ratios of Standard Angles [Including Evaluation of an Expression Involving Trigonometric Ratios]
Exercise 23 (C) | Q 11.3 | Page 298
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