English

Find angle A, if sec 2A = cosec (A + 48°).

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Question

Find angle A, if sec 2A = cosec (A + 48°).

Sum
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Solution

Given:

sec 2A = cosec (A + 48°)

Formula:

sec(90° − θ) = csc(θ)

Solution:

csc(90° − 2A) = csc(A + 48°)  [Using the complementary relation sec 2A = csc(90° − 2A)]

90° − 2A = A + 48°  [Equating the angles of equal cosecant functions]

90° − 48° = 2A + A  [Rearranging terms to group like quantities]

42° = 3A  [Simplifying both sides of the equation]

3A = 42°  [Reversing the equation for clarity]

\[A = \frac{42^\circ}{3}\]  [Dividing both sides by 3]

A = 14°  [Simplifying the division]

∴ A = 14°

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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 13. | Page 335
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