Math, asked by tatsat22, 10 months ago

f(x) denotes the sum of infinite terms with of series
1- cosx +cos^2x - cos^3x + cos^4x —-----------------(x not equal to nπ)

& g(x) denotes the sum of infinite terms of series
1 + since + sin^2x + sin^3x + ————————(x is not equal to (2n+1)π/2)

Find all possible values are f x for which f(x) = g(x )​

Answers

Answered by amitnrw
0

x  = (4n - 1)π/4  

Step-by-step explanation:

f(x)  = 1 - Cosx  + Cos²x  - Cos³x + Cos⁴x  -   +.......................

this is an GP

a = 1

r = -Cosx

Sum  = a/(1 - r)    = 1/(1 - (-Cosx)) = 1/(1 + Cosx)

g(x)  = 1 + Sinx  + Sin²x  + Sin³x + Sin⁴x  -   +.......................

this is an GP

a = 1

r = Sinx

Sum  = a/(1 - r)    = 1/(1 - Sinx)

f(x) = g(x)

=> 1/(1 + Cosx) = 1/(1 - Sinx)

=> 1- Sinx = 1 + Cosx

=> Cosx  + Sinx  = 0

=>Squaring both sides

=> Cos²x + Sin²x + 2SinxCosx = 0

=> 1 + Sin2x = 0

=>  Sin2x = - 1

=> 2x  =  2nπ - π/2

=> 2x = (4nπ - π)/2

=> x  = (4n - 1)π/4

for x = (4n - 1)π/4  f(x) = gx

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