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Solve for x : sin2 60° + cos2 (3x- 9°) = 1

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Question

Solve for x : sin2 60° + cos2 (3x- 9°) = 1

Sum
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Solution

sin260° + cos2(3x – 9°) = 1
cos2(3x – 9°) = 1 – sin260°
cos2(3x – 9°) = 1 – `(3)/(4)`
cos2(3x – 9°) = `(1)/(4)`
cos2(3x – 9°) = `(1)/(2)`
3x – 9° = 60°
3x = 69°
x = 23°



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Trigonometric Equation Problem and Solution
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Chapter 21: Trigonometrical Ratios [Sine, Consine, Tangent of an Angle and their Reciprocals] - TEST YOURSELF [Page 335]

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Selina Concise Mathematics [English] Class 9 ICSE
Chapter 21 Trigonometrical Ratios [Sine, Consine, Tangent of an Angle and their Reciprocals]
TEST YOURSELF | Q 7. (xii) | Page 335
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