the answer is π/2 + 2nπ
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cos^2(x) = -2sin(x) + 2
use the fact that sin^2(x) + cos^2(x) = 1 ==> cos^2(x) = 1 - sin^2(x)
=> 1 - sin^2(x) = -2sin(x) + 2
rearranging gives
=> sin^2(x) - 2sin(x) + 1 = 0
factorize
=> (sin x - 1)^2 = 0
==>sin x = 1
x = π/2 and (π/2 + 2nπ) where n is any integer
use the fact that sin^2(x) + cos^2(x) = 1 ==> cos^2(x) = 1 - sin^2(x)
=> 1 - sin^2(x) = -2sin(x) + 2
rearranging gives
=> sin^2(x) - 2sin(x) + 1 = 0
factorize
=> (sin x - 1)^2 = 0
==>sin x = 1
x = π/2 and (π/2 + 2nπ) where n is any integer
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1 - sin²x = -2sin x + 2
sin²x - 2sin x + 1 = (sin x - 1)^2 = 0
sin x = 1
x = π/2 + 2nπ
sin²x - 2sin x + 1 = (sin x - 1)^2 = 0
sin x = 1
x = π/2 + 2nπ