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In the case, given below, find the value of angle A, where 0° ≤ A ≤ 90°. cos(90° - A) · sec 77° = 1

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Question

In the case, given below, find the value of angle A, where 0° ≤ A ≤ 90°.

cos(90° - A) · sec 77° = 1

Sum
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Solution

cos (90° - A) · sec 77° = 1

⇒ cos(90° - A) = `1/(sec 77°)`

⇒ cos(90° - A) = cos 77°

⇒ 90° - A = 77°

⇒ - A = 77° - 90°
⇒ - A = - 13°
⇒ A = 13°

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Chapter 21: Trigonometrical Ratios [Sine, Consine, Tangent of an Angle and their Reciprocals] - EXERCISE 21 (F) [Page 334]

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Selina Concise Mathematics [English] Class 9 ICSE
Chapter 21 Trigonometrical Ratios [Sine, Consine, Tangent of an Angle and their Reciprocals]
EXERCISE 21 (F) | Q 9. (ii) | Page 334
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