SOLUTION: sin4x-2sin2x-1=0

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Question 799273: sin4x-2sin2x-1=0
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
solve for x
sin^4x-2sin^2x-1=0
let u=sin^2x
u^2=sin^4x
u^2-2u-1=0
solve for u with quadratic formula:
u+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a=1. b=-2, c=-1
ans:
u≈-0.4142(reject)
or
u≈2.4142
..
sin^2x=2.4142
x=±√2.4142≈±1.5537(radians)