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Number of solutions of the equation tanx + secx = 2 cosx lying in the interval [0, 2π] is ______.

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Question

Number of solutions of the equation tan x + sec x = 2 cosx lying in the interval [0, 2π] is ______.

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Solution

Number of solutions of the equation tan x + sec x = 2 cosx lying in the interval [0, 2π] is 3.

Explanation:

tanx + sec = 2cosx

sin + 1 = cos2x = sinx + 1= 2 -  sin2x

2sin2x + sinx -1 = 0

(2sinx - 1) (sin + 1) = 0

but sinx = -1 

`x= (3pi)/2`

`sinx = 1/2 = sin(pi/6)`

therefore the general solution is,

`x = npi + (-1)^n.pi/6`

`x = ...pi/6, (5pi)/6`

therefore, the number of solutions in the given interval is 3. 

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Chapter 3: Trigonometric Functions - Exercise [Page 58]

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NCERT Exemplar Mathematics Exemplar [English] Class 11
Chapter 3 Trigonometric Functions
Exercise | Q 53 | Page 58

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